WordPress 4.3
[autoinstalls/wordpress.git] / wp-admin / includes / class-wp-upgrader.php
index ef8fb5f884f8fc14158f95dfad926d9b0f0efc5d..235df514c1716888f480c0c59f8f5702ab33c007 100644 (file)
  *
  * This set of classes are designed to be used to upgrade/install a local set of files on the filesystem via the Filesystem Abstraction classes.
  *
  *
  * This set of classes are designed to be used to upgrade/install a local set of files on the filesystem via the Filesystem Abstraction classes.
  *
- * @link http://trac.wordpress.org/ticket/7875 consolidate plugin/theme/core upgrade/install functions
+ * @link https://core.trac.wordpress.org/ticket/7875 consolidate plugin/theme/core upgrade/install functions
  *
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 
  *
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 
+require ABSPATH . 'wp-admin/includes/class-wp-upgrader-skins.php';
+
 /**
  * WordPress Upgrader class for Upgrading/Installing a local set of files via the Filesystem Abstraction classes from a Zip file.
  *
 /**
  * WordPress Upgrader class for Upgrading/Installing a local set of files via the Filesystem Abstraction classes from a Zip file.
  *
- * @TODO More Detailed docs, for methods as well.
- *
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 class WP_Upgrader {
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 class WP_Upgrader {
-       var $strings = array();
-       var $skin = null;
-       var $result = array();
 
 
-       function __construct($skin = null) {
+       /**
+        * The error/notification strings used to update the user on the progress.
+        *
+        * @since 2.8.0
+        * @var string $strings
+        */
+       public $strings = array();
+
+       /**
+        * The upgrader skin being used.
+        *
+        * @since 2.8.0
+        * @var WP_Upgrader_Skin $skin
+        */
+       public $skin = null;
+
+       /**
+        * The result of the installation.
+        *
+        * This is set by {@see WP_Upgrader::install_package()}, only when the package is installed
+        * successfully. It will then be an array, unless a {@see WP_Error} is returned by the
+        * {@see 'upgrader_post_install'} filter. In that case, the `WP_Error` will be assigned to
+        * it.
+        *
+        * @since 2.8.0
+        * @var WP_Error|array $result {
+        *      @type string $source             The full path to the source the files were installed from.
+        *      @type string $source_files       List of all the files in the source directory.
+        *      @type string $destination        The full path to the install destination folder.
+        *      @type string $destination_name   The name of the destination folder, or empty if `$destination`
+        *                                       and `$local_destination` are the same.
+        *      @type string $local_destination  The full local path to the destination folder. This is usually
+        *                                       the same as `$destination`.
+        *      @type string $remote_destination The full remote path to the destination folder
+        *                                       (i.e., from `$wp_filesystem`).
+        *      @type bool   $clear_destination  Whether the destination folder was cleared.
+        * }
+        */
+       public $result = array();
+
+       /**
+        * The total number of updates being performed.
+        *
+        * Set by the bulk update methods.
+        *
+        * @since 3.0.0
+        * @var int $update_count
+        */
+       public $update_count = 0;
+
+       /**
+        * The current update if multiple updates are being performed.
+        *
+        * Used by the bulk update methods, and incremented for each update.
+        *
+        * @since 3.0.0
+        * @var int
+        */
+       public $update_current = 0;
+
+       /**
+        * Construct the upgrader with a skin.
+        *
+        * @since 2.8.0
+        *
+        * @param WP_Upgrader_Skin $skin The upgrader skin to use. Default is a {@see WP_Upgrader_Skin}
+        *                               instance.
+        */
+       public function __construct( $skin = null ) {
                if ( null == $skin )
                        $this->skin = new WP_Upgrader_Skin();
                else
                        $this->skin = $skin;
        }
 
                if ( null == $skin )
                        $this->skin = new WP_Upgrader_Skin();
                else
                        $this->skin = $skin;
        }
 
-       function init() {
+       /**
+        * Initialize the upgrader.
+        *
+        * This will set the relationship between the skin being used and this upgrader,
+        * and also add the generic strings to `WP_Upgrader::$strings`.
+        *
+        * @since 2.8.0
+        */
+       public function init() {
                $this->skin->set_upgrader($this);
                $this->generic_strings();
        }
 
                $this->skin->set_upgrader($this);
                $this->generic_strings();
        }
 
-       function generic_strings() {
+       /**
+        * Add the generic strings to WP_Upgrader::$strings.
+        *
+        * @since 2.8.0
+        */
+       public function generic_strings() {
                $this->strings['bad_request'] = __('Invalid Data provided.');
                $this->strings['fs_unavailable'] = __('Could not access filesystem.');
                $this->strings['fs_error'] = __('Filesystem error.');
                $this->strings['bad_request'] = __('Invalid Data provided.');
                $this->strings['fs_unavailable'] = __('Could not access filesystem.');
                $this->strings['fs_error'] = __('Filesystem error.');
@@ -50,25 +128,43 @@ class WP_Upgrader {
 
                $this->strings['download_failed'] = __('Download failed.');
                $this->strings['installing_package'] = __('Installing the latest version…');
 
                $this->strings['download_failed'] = __('Download failed.');
                $this->strings['installing_package'] = __('Installing the latest version…');
+               $this->strings['no_files'] = __('The package contains no files.');
                $this->strings['folder_exists'] = __('Destination folder already exists.');
                $this->strings['mkdir_failed'] = __('Could not create directory.');
                $this->strings['incompatible_archive'] = __('The package could not be installed.');
                $this->strings['folder_exists'] = __('Destination folder already exists.');
                $this->strings['mkdir_failed'] = __('Could not create directory.');
                $this->strings['incompatible_archive'] = __('The package could not be installed.');
+               $this->strings['files_not_writable'] = __( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' );
 
                $this->strings['maintenance_start'] = __('Enabling Maintenance mode…');
                $this->strings['maintenance_end'] = __('Disabling Maintenance mode…');
        }
 
 
                $this->strings['maintenance_start'] = __('Enabling Maintenance mode…');
                $this->strings['maintenance_end'] = __('Disabling Maintenance mode…');
        }
 
-       function fs_connect( $directories = array() ) {
+       /**
+        * Connect to the filesystem.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param array $directories                  Optional. A list of directories. If any of these do
+        *                                            not exist, a {@see WP_Error} object will be returned.
+        *                                            Default empty array.
+        * @param bool  $allow_relaxed_file_ownership Whether to allow relaxed file ownership.
+        *                                            Default false.
+        * @return bool|WP_Error True if able to connect, false or a {@see WP_Error} otherwise.
+        */
+       public function fs_connect( $directories = array(), $allow_relaxed_file_ownership = false ) {
                global $wp_filesystem;
 
                global $wp_filesystem;
 
-               if ( false === ($credentials = $this->skin->request_filesystem_credentials()) )
+               if ( false === ( $credentials = $this->skin->request_filesystem_credentials( false, $directories[0], $allow_relaxed_file_ownership ) ) ) {
                        return false;
                        return false;
+               }
 
 
-               if ( ! WP_Filesystem($credentials) ) {
+               if ( ! WP_Filesystem( $credentials, $directories[0], $allow_relaxed_file_ownership ) ) {
                        $error = true;
                        if ( is_object($wp_filesystem) && $wp_filesystem->errors->get_error_code() )
                                $error = $wp_filesystem->errors;
                        $error = true;
                        if ( is_object($wp_filesystem) && $wp_filesystem->errors->get_error_code() )
                                $error = $wp_filesystem->errors;
-                       $this->skin->request_filesystem_credentials($error); //Failed to connect, Error and request again
+                       // Failed to connect, Error and request again
+                       $this->skin->request_filesystem_credentials( $error, $directories[0], $allow_relaxed_file_ownership );
                        return false;
                }
 
                        return false;
                }
 
@@ -92,20 +188,43 @@ class WP_Upgrader {
                                        if ( ! $wp_filesystem->wp_plugins_dir() )
                                                return new WP_Error('fs_no_plugins_dir', $this->strings['fs_no_plugins_dir']);
                                        break;
                                        if ( ! $wp_filesystem->wp_plugins_dir() )
                                                return new WP_Error('fs_no_plugins_dir', $this->strings['fs_no_plugins_dir']);
                                        break;
-                               case WP_CONTENT_DIR . '/themes':
-                                       if ( ! $wp_filesystem->find_folder(WP_CONTENT_DIR . '/themes') )
+                               case get_theme_root():
+                                       if ( ! $wp_filesystem->wp_themes_dir() )
                                                return new WP_Error('fs_no_themes_dir', $this->strings['fs_no_themes_dir']);
                                        break;
                                default:
                                        if ( ! $wp_filesystem->find_folder($dir) )
                                                return new WP_Error('fs_no_themes_dir', $this->strings['fs_no_themes_dir']);
                                        break;
                                default:
                                        if ( ! $wp_filesystem->find_folder($dir) )
-                                               return new WP_Error('fs_no_folder', sprintf($this->strings['fs_no_folder'], $dir));
+                                               return new WP_Error( 'fs_no_folder', sprintf( $this->strings['fs_no_folder'], esc_html( basename( $dir ) ) ) );
                                        break;
                        }
                }
                return true;
        } //end fs_connect();
 
                                        break;
                        }
                }
                return true;
        } //end fs_connect();
 
-       function download_package($package) {
+       /**
+        * Download a package.
+        *
+        * @since 2.8.0
+        *
+        * @param string $package The URI of the package. If this is the full path to an
+        *                        existing local file, it will be returned untouched.
+        * @return string|WP_Error The full path to the downloaded package file, or a {@see WP_Error} object.
+        */
+       public function download_package( $package ) {
+
+               /**
+                * Filter whether to return the package.
+                *
+                * @since 3.7.0
+                *
+                * @param bool        $reply   Whether to bail without returning the package.
+                *                             Default false.
+                * @param string      $package The package file name.
+                * @param WP_Upgrader $this    The WP_Upgrader instance.
+                */
+               $reply = apply_filters( 'upgrader_pre_download', false, $package, $this );
+               if ( false !== $reply )
+                       return $reply;
 
                if ( ! preg_match('!^(http|https|ftp)://!i', $package) && file_exists($package) ) //Local file or remote?
                        return $package; //must be a local file..
 
                if ( ! preg_match('!^(http|https|ftp)://!i', $package) && file_exists($package) ) //Local file or remote?
                        return $package; //must be a local file..
@@ -123,7 +242,19 @@ class WP_Upgrader {
                return $download_file;
        }
 
                return $download_file;
        }
 
-       function unpack_package($package, $delete_package = true) {
+       /**
+        * Unpack a compressed package file.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $package        Full path to the package file.
+        * @param bool   $delete_package Optional. Whether to delete the package file after attempting
+        *                               to unpack it. Default true.
+        * @return string|WP_Error The path to the unpacked contents, or a {@see WP_Error} on failure.
+        */
+       public function unpack_package( $package, $delete_package = true ) {
                global $wp_filesystem;
 
                $this->skin->feedback('unpack_package');
                global $wp_filesystem;
 
                $this->skin->feedback('unpack_package');
@@ -137,15 +268,15 @@ class WP_Upgrader {
                                $wp_filesystem->delete($upgrade_folder . $file['name'], true);
                }
 
                                $wp_filesystem->delete($upgrade_folder . $file['name'], true);
                }
 
-               //We need a working directory
-               $working_dir = $upgrade_folder . basename($package, '.zip');
+               // We need a working directory - Strip off any .tmp or .zip suffixes
+               $working_dir = $upgrade_folder . basename( basename( $package, '.tmp' ), '.zip' );
 
                // Clean up working directory
                if ( $wp_filesystem->is_dir($working_dir) )
                        $wp_filesystem->delete($working_dir, true);
 
                // Unzip package to working directory
 
                // Clean up working directory
                if ( $wp_filesystem->is_dir($working_dir) )
                        $wp_filesystem->delete($working_dir, true);
 
                // Unzip package to working directory
-               $result = unzip_file($package, $working_dir); //TODO optimizations, Copy when Move/Rename would suffice?
+               $result = unzip_file( $package, $working_dir );
 
                // Once extracted, delete the package if required.
                if ( $delete_package )
 
                // Once extracted, delete the package if required.
                if ( $delete_package )
@@ -162,69 +293,211 @@ class WP_Upgrader {
                return $working_dir;
        }
 
                return $working_dir;
        }
 
-       function install_package($args = array()) {
+       /**
+        * Clears the directory where this item is going to be installed into.
+        *
+        * @since 4.3.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $remote_destination The location on the remote filesystem to be cleared
+        * @return bool|WP_Error True upon success, WP_Error on failure.
+        */
+       public function clear_destination( $remote_destination ) {
                global $wp_filesystem;
                global $wp_filesystem;
-               $defaults = array( 'source' => '', 'destination' => '', //Please always pass these
-                                               'clear_destination' => false, 'clear_working' => false,
-                                               'hook_extra' => array());
 
 
-               $args = wp_parse_args($args, $defaults);
-               extract($args);
+               if ( ! $wp_filesystem->exists( $remote_destination ) ) {
+                       return true;
+               }
 
 
-               @set_time_limit( 300 );
+               // Check all files are writable before attempting to clear the destination.
+               $unwritable_files = array();
 
 
-               if ( empty($source) || empty($destination) )
-                       return new WP_Error('bad_request', $this->strings['bad_request']);
+               $_files = $wp_filesystem->dirlist( $remote_destination, true, true );
+
+               // Flatten the resulting array, iterate using each as we append to the array during iteration.
+               while ( $f = each( $_files ) ) {
+                       $file = $f['value'];
+                       $name = $f['key'];
+
+                       if ( ! isset( $file['files'] ) ) {
+                               continue;
+                       }
+
+                       foreach ( $file['files'] as $filename => $details ) {
+                               $_files[ $name . '/' . $filename ] = $details;
+                       }
+               }
+
+               // Check writability.
+               foreach ( $_files as $filename => $file_details ) {
+                       if ( ! $wp_filesystem->is_writable( $remote_destination . $filename ) ) {
+
+                               // Attempt to alter permissions to allow writes and try again.
+                               $wp_filesystem->chmod( $remote_destination . $filename, ( 'd' == $file_details['type'] ? FS_CHMOD_DIR : FS_CHMOD_FILE ) );
+                               if ( ! $wp_filesystem->is_writable( $remote_destination . $filename ) ) {
+                                       $unwritable_files[] = $filename;
+                               }
+                       }
+               }
+
+               if ( ! empty( $unwritable_files ) ) {
+                       return new WP_Error( 'files_not_writable', $this->strings['files_not_writable'], implode( ', ', $unwritable_files ) );
+               }
+
+               if ( ! $wp_filesystem->delete( $remote_destination, true ) ) {
+                       return new WP_Error( 'remove_old_failed', $this->strings['remove_old_failed'] );
+               }
+
+               return true;
+       }
+
+       /**
+        * Install a package.
+        *
+        * Copies the contents of a package form a source directory, and installs them in
+        * a destination directory. Optionally removes the source. It can also optionally
+        * clear out the destination folder if it already exists.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        * @global array              $wp_theme_directories
+        *
+        * @param array|string $args {
+        *     Optional. Array or string of arguments for installing a package. Default empty array.
+        *
+        *     @type string $source                      Required path to the package source. Default empty.
+        *     @type string $destination                 Required path to a folder to install the package in.
+        *                                               Default empty.
+        *     @type bool   $clear_destination           Whether to delete any files already in the destination
+        *                                               folder. Default false.
+        *     @type bool   $clear_working               Whether to delete the files form the working directory
+        *                                               after copying to the destination. Default false.
+        *     @type bool   $abort_if_destination_exists Whether to abort the installation if
+        *                                               the destination folder already exists. Default true.
+        *     @type array  $hook_extra                  Extra arguments to pass to the filter hooks called by
+        *                                               {@see WP_Upgrader::install_package()}. Default empty array.
+        * }
+        *
+        * @return array|WP_Error The result (also stored in `WP_Upgrader:$result`), or a {@see WP_Error} on failure.
+        */
+       public function install_package( $args = array() ) {
+               global $wp_filesystem, $wp_theme_directories;
+
+               $defaults = array(
+                       'source' => '', // Please always pass this
+                       'destination' => '', // and this
+                       'clear_destination' => false,
+                       'clear_working' => false,
+                       'abort_if_destination_exists' => true,
+                       'hook_extra' => array()
+               );
+
+               $args = wp_parse_args($args, $defaults);
+
+               // These were previously extract()'d.
+               $source = $args['source'];
+               $destination = $args['destination'];
+               $clear_destination = $args['clear_destination'];
 
 
-               $this->skin->feedback('installing_package');
+               @set_time_limit( 300 );
 
 
-               $res = apply_filters('upgrader_pre_install', true, $hook_extra);
-               if ( is_wp_error($res) )
+               if ( empty( $source ) || empty( $destination ) ) {
+                       return new WP_Error( 'bad_request', $this->strings['bad_request'] );
+               }
+               $this->skin->feedback( 'installing_package' );
+
+               /**
+                * Filter the install response before the installation has started.
+                *
+                * Returning a truthy value, or one that could be evaluated as a WP_Error
+                * will effectively short-circuit the installation, returning that value
+                * instead.
+                *
+                * @since 2.8.0
+                *
+                * @param bool|WP_Error $response   Response.
+                * @param array         $hook_extra Extra arguments passed to hooked filters.
+                */
+               $res = apply_filters( 'upgrader_pre_install', true, $args['hook_extra'] );
+               if ( is_wp_error( $res ) ) {
                        return $res;
                        return $res;
+               }
 
                //Retain the Original source and destinations
 
                //Retain the Original source and destinations
-               $remote_source = $source;
+               $remote_source = $args['source'];
                $local_destination = $destination;
 
                $local_destination = $destination;
 
-               $source_files = array_keys( $wp_filesystem->dirlist($remote_source) );
-               $remote_destination = $wp_filesystem->find_folder($local_destination);
+               $source_files = array_keys( $wp_filesystem->dirlist( $remote_source ) );
+               $remote_destination = $wp_filesystem->find_folder( $local_destination );
 
                //Locate which directory to copy to the new folder, This is based on the actual folder holding the files.
 
                //Locate which directory to copy to the new folder, This is based on the actual folder holding the files.
-               if ( 1 == count($source_files) && $wp_filesystem->is_dir( trailingslashit($source) . $source_files[0] . '/') ) //Only one folder? Then we want its contents.
-                       $source = trailingslashit($source) . trailingslashit($source_files[0]);
-               elseif ( count($source_files) == 0 )
-                       return new WP_Error( 'incompatible_archive', $this->strings['incompatible_archive'], __( 'The plugin contains no files.' ) ); //There are no files?
-               else //Its only a single file, The upgrader will use the foldername of this file as the destination folder. foldername is based on zip filename.
-                       $source = trailingslashit($source);
-
-               //Hook ability to change the source file location..
-               $source = apply_filters('upgrader_source_selection', $source, $remote_source, $this);
-               if ( is_wp_error($source) )
-                       return $source;
+               if ( 1 == count( $source_files ) && $wp_filesystem->is_dir( trailingslashit( $args['source'] ) . $source_files[0] . '/' ) ) { //Only one folder? Then we want its contents.
+                       $source = trailingslashit( $args['source'] ) . trailingslashit( $source_files[0] );
+               } elseif ( count( $source_files ) == 0 ) {
+                       return new WP_Error( 'incompatible_archive_empty', $this->strings['incompatible_archive'], $this->strings['no_files'] ); // There are no files?
+               } else { //It's only a single file, the upgrader will use the foldername of this file as the destination folder. foldername is based on zip filename.
+                       $source = trailingslashit( $args['source'] );
+               }
 
 
-               //Has the source location changed? If so, we need a new source_files list.
-               if ( $source !== $remote_source )
-                       $source_files = array_keys( $wp_filesystem->dirlist($source) );
+               /**
+                * Filter the source file location for the upgrade package.
+                *
+                * @since 2.8.0
+                *
+                * @param string      $source        File source location.
+                * @param string      $remote_source Remove file source location.
+                * @param WP_Upgrader $this          WP_Upgrader instance.
+                */
+               $source = apply_filters( 'upgrader_source_selection', $source, $remote_source, $this );
+               if ( is_wp_error( $source ) ) {
+                       return $source;
+               }
 
 
-               //Protection against deleting files in any important base directories.
-               if ( in_array( $destination, array(ABSPATH, WP_CONTENT_DIR, WP_PLUGIN_DIR, WP_CONTENT_DIR . '/themes') ) ) {
-                       $remote_destination = trailingslashit($remote_destination) . trailingslashit(basename($source));
-                       $destination = trailingslashit($destination) . trailingslashit(basename($source));
+               // Has the source location changed? If so, we need a new source_files list.
+               if ( $source !== $remote_source ) {
+                       $source_files = array_keys( $wp_filesystem->dirlist( $source ) );
+               }
+               /*
+                * Protection against deleting files in any important base directories.
+                * Theme_Upgrader & Plugin_Upgrader also trigger this, as they pass the
+                * destination directory (WP_PLUGIN_DIR / wp-content/themes) intending
+                * to copy the directory into the directory, whilst they pass the source
+                * as the actual files to copy.
+                */
+               $protected_directories = array( ABSPATH, WP_CONTENT_DIR, WP_PLUGIN_DIR, WP_CONTENT_DIR . '/themes' );
+
+               if ( is_array( $wp_theme_directories ) ) {
+                       $protected_directories = array_merge( $protected_directories, $wp_theme_directories );
+               }
+               if ( in_array( $destination, $protected_directories ) ) {
+                       $remote_destination = trailingslashit( $remote_destination ) . trailingslashit( basename( $source ) );
+                       $destination = trailingslashit( $destination ) . trailingslashit( basename( $source ) );
                }
 
                if ( $clear_destination ) {
                }
 
                if ( $clear_destination ) {
-                       //We're going to clear the destination if there's something there
+                       // We're going to clear the destination if there's something there
                        $this->skin->feedback('remove_old');
                        $this->skin->feedback('remove_old');
-                       $removed = true;
-                       if ( $wp_filesystem->exists($remote_destination) )
-                               $removed = $wp_filesystem->delete($remote_destination, true);
-                       $removed = apply_filters('upgrader_clear_destination', $removed, $local_destination, $remote_destination, $hook_extra);
 
 
-                       if ( is_wp_error($removed) )
+                       $removed = $this->clear_destination( $remote_destination );
+
+                       /**
+                        * Filter whether the upgrader cleared the destination.
+                        *
+                        * @since 2.8.0
+                        *
+                        * @param mixed  $removed            Whether the destination was cleared. true on success, WP_Error on failure
+                        * @param string $local_destination  The local package destination.
+                        * @param string $remote_destination The remote package destination.
+                        * @param array  $hook_extra         Extra arguments passed to hooked filters.
+                        */
+                       $removed = apply_filters( 'upgrader_clear_destination', $removed, $local_destination, $remote_destination, $args['hook_extra'] );
+
+                       if ( is_wp_error( $removed ) ) {
                                return $removed;
                                return $removed;
-                       else if ( ! $removed )
-                               return new WP_Error('remove_old_failed', $this->strings['remove_old_failed']);
-               } elseif ( $wp_filesystem->exists($remote_destination) ) {
+                       }
+               } elseif ( $args['abort_if_destination_exists'] && $wp_filesystem->exists($remote_destination) ) {
                        //If we're not clearing the destination folder and something exists there already, Bail.
                        //But first check to see if there are actually any files in the folder.
                        $_files = $wp_filesystem->dirlist($remote_destination);
                        //If we're not clearing the destination folder and something exists there already, Bail.
                        //But first check to see if there are actually any files in the folder.
                        $_files = $wp_filesystem->dirlist($remote_destination);
@@ -235,29 +508,43 @@ class WP_Upgrader {
                }
 
                //Create destination if needed
                }
 
                //Create destination if needed
-               if ( !$wp_filesystem->exists($remote_destination) )
-                       if ( !$wp_filesystem->mkdir($remote_destination, FS_CHMOD_DIR) )
-                               return new WP_Error('mkdir_failed', $this->strings['mkdir_failed'], $remote_destination);
-
+               if ( ! $wp_filesystem->exists( $remote_destination ) ) {
+                       if ( ! $wp_filesystem->mkdir( $remote_destination, FS_CHMOD_DIR ) ) {
+                               return new WP_Error( 'mkdir_failed_destination', $this->strings['mkdir_failed'], $remote_destination );
+                       }
+               }
                // Copy new version of item into place.
                $result = copy_dir($source, $remote_destination);
                if ( is_wp_error($result) ) {
                // Copy new version of item into place.
                $result = copy_dir($source, $remote_destination);
                if ( is_wp_error($result) ) {
-                       if ( $clear_working )
-                               $wp_filesystem->delete($remote_source, true);
+                       if ( $args['clear_working'] ) {
+                               $wp_filesystem->delete( $remote_source, true );
+                       }
                        return $result;
                }
 
                //Clear the Working folder?
                        return $result;
                }
 
                //Clear the Working folder?
-               if ( $clear_working )
-                       $wp_filesystem->delete($remote_source, true);
+               if ( $args['clear_working'] ) {
+                       $wp_filesystem->delete( $remote_source, true );
+               }
 
                $destination_name = basename( str_replace($local_destination, '', $destination) );
 
                $destination_name = basename( str_replace($local_destination, '', $destination) );
-               if ( '.' == $destination_name )
+               if ( '.' == $destination_name ) {
                        $destination_name = '';
                        $destination_name = '';
+               }
+
+               $this->result = compact( 'source', 'source_files', 'destination', 'destination_name', 'local_destination', 'remote_destination', 'clear_destination' );
 
 
-               $this->result = compact('local_source', 'source', 'source_name', 'source_files', 'destination', 'destination_name', 'local_destination', 'remote_destination', 'clear_destination', 'delete_source_dir');
+               /**
+                * Filter the install response after the installation has finished.
+                *
+                * @since 2.8.0
+                *
+                * @param bool  $response   Install response.
+                * @param array $hook_extra Extra arguments passed to hooked filters.
+                * @param array $result     Installation result data.
+                */
+               $res = apply_filters( 'upgrader_post_install', true, $args['hook_extra'], $this->result );
 
 
-               $res = apply_filters('upgrader_post_install', true, $hook_extra, $this->result);
                if ( is_wp_error($res) ) {
                        $this->result = $res;
                        return $res;
                if ( is_wp_error($res) ) {
                        $this->result = $res;
                        return $res;
@@ -267,60 +554,132 @@ class WP_Upgrader {
                return $this->result;
        }
 
                return $this->result;
        }
 
-       function run($options) {
-
-               $defaults = array(      'package' => '', //Please always pass this.
-                                                       'destination' => '', //And this
-                                                       'clear_destination' => false,
-                                                       'clear_working' => true,
-                                                       'is_multi' => false,
-                                                       'hook_extra' => array() //Pass any extra $hook_extra args here, this will be passed to any hooked filters.
-                                               );
+       /**
+        * Run an upgrade/install.
+        *
+        * Attempts to download the package (if it is not a local file), unpack it, and
+        * install it in the destination folder.
+        *
+        * @since 2.8.0
+        *
+        * @param array $options {
+        *     Array or string of arguments for upgrading/installing a package.
+        *
+        *     @type string $package                     The full path or URI of the package to install.
+        *                                               Default empty.
+        *     @type string $destination                 The full path to the destination folder.
+        *                                               Default empty.
+        *     @type bool   $clear_destination           Whether to delete any files already in the
+        *                                               destination folder. Default false.
+        *     @type bool   $clear_working               Whether to delete the files form the working
+        *                                               directory after copying to the destination.
+        *                                               Default false.
+        *     @type bool   $abort_if_destination_exists Whether to abort the installation if the destination
+        *                                               folder already exists. When true, `$clear_destination`
+        *                                               should be false. Default true.
+        *     @type bool   $is_multi                    Whether this run is one of multiple upgrade/install
+        *                                               actions being performed in bulk. When true, the skin
+        *                                               {@see WP_Upgrader::header()} and {@see WP_Upgrader::footer()}
+        *                                               aren't called. Default false.
+        *     @type array  $hook_extra                  Extra arguments to pass to the filter hooks called by
+        *                                               {@see WP_Upgrader::run()}.
+        * }
+        *
+        * @return array|false|WP_error The result from self::install_package() on success, otherwise a WP_Error,
+        *                              or false if unable to connect to the filesystem.
+        */
+       public function run( $options ) {
+
+               $defaults = array(
+                       'package' => '', // Please always pass this.
+                       'destination' => '', // And this
+                       'clear_destination' => false,
+                       'abort_if_destination_exists' => true, // Abort if the Destination directory exists, Pass clear_destination as false please
+                       'clear_working' => true,
+                       'is_multi' => false,
+                       'hook_extra' => array() // Pass any extra $hook_extra args here, this will be passed to any hooked filters.
+               );
 
 
-               $options = wp_parse_args($options, $defaults);
-               extract($options);
+               $options = wp_parse_args( $options, $defaults );
+
+               /**
+                * Filter the package options before running an update.
+                *
+                * @since 4.3.0
+                *
+                * @param array $options {
+                *     Options used by the upgrader.
+                *
+                *     @type string $package                     Package for update.
+                *     @type string $destination                 Update location.
+                *     @type bool   $clear_destination           Clear the destination resource.
+                *     @type bool   $clear_working               Clear the working resource.
+                *     @type bool   $abort_if_destination_exists Abort if the Destination directory exists.
+                *     @type bool   $is_multi                    Whether the upgrader is running multiple times.
+                *     @type array  $hook_extra                  Extra hook arguments.
+                * }
+                */
+               $options = apply_filters( 'upgrader_package_options', $options );
+
+               if ( ! $options['is_multi'] ) { // call $this->header separately if running multiple times
+                       $this->skin->header();
+               }
 
 
-               //Connect to the Filesystem first.
-               $res = $this->fs_connect( array(WP_CONTENT_DIR, $destination) );
-               if ( ! $res ) //Mainly for non-connected filesystem.
+               // Connect to the Filesystem first.
+               $res = $this->fs_connect( array( WP_CONTENT_DIR, $options['destination'] ) );
+               // Mainly for non-connected filesystem.
+               if ( ! $res ) {
+                       if ( ! $options['is_multi'] ) {
+                               $this->skin->footer();
+                       }
                        return false;
                        return false;
+               }
+
+               $this->skin->before();
 
                if ( is_wp_error($res) ) {
                        $this->skin->error($res);
 
                if ( is_wp_error($res) ) {
                        $this->skin->error($res);
+                       $this->skin->after();
+                       if ( ! $options['is_multi'] ) {
+                               $this->skin->footer();
+                       }
                        return $res;
                }
 
                        return $res;
                }
 
-               if ( !$is_multi ) // call $this->header separately if running multiple times
-                       $this->skin->header();
-
-               $this->skin->before();
-
                //Download the package (Note, This just returns the filename of the file if the package is a local file)
                //Download the package (Note, This just returns the filename of the file if the package is a local file)
-               $download = $this->download_package( $package );
+               $download = $this->download_package( $options['package'] );
                if ( is_wp_error($download) ) {
                        $this->skin->error($download);
                        $this->skin->after();
                if ( is_wp_error($download) ) {
                        $this->skin->error($download);
                        $this->skin->after();
+                       if ( ! $options['is_multi'] ) {
+                               $this->skin->footer();
+                       }
                        return $download;
                }
 
                        return $download;
                }
 
-               $delete_package = ($download != $package); // Do not delete a "local" file
+               $delete_package = ( $download != $options['package'] ); // Do not delete a "local" file
 
                //Unzips the file into a temporary directory
                $working_dir = $this->unpack_package( $download, $delete_package );
                if ( is_wp_error($working_dir) ) {
                        $this->skin->error($working_dir);
                        $this->skin->after();
 
                //Unzips the file into a temporary directory
                $working_dir = $this->unpack_package( $download, $delete_package );
                if ( is_wp_error($working_dir) ) {
                        $this->skin->error($working_dir);
                        $this->skin->after();
+                       if ( ! $options['is_multi'] ) {
+                               $this->skin->footer();
+                       }
                        return $working_dir;
                }
 
                //With the given options, this installs it to the destination directory.
                $result = $this->install_package( array(
                        return $working_dir;
                }
 
                //With the given options, this installs it to the destination directory.
                $result = $this->install_package( array(
-                                                                                       'source' => $working_dir,
-                                                                                       'destination' => $destination,
-                                                                                       'clear_destination' => $clear_destination,
-                                                                                       'clear_working' => $clear_working,
-                                                                                       'hook_extra' => $hook_extra
-                                                                               ) );
+                       'source' => $working_dir,
+                       'destination' => $options['destination'],
+                       'clear_destination' => $options['clear_destination'],
+                       'abort_if_destination_exists' => $options['abort_if_destination_exists'],
+                       'clear_working' => $options['clear_working'],
+                       'hook_extra' => $options['hook_extra']
+               ) );
+
                $this->skin->set_result($result);
                if ( is_wp_error($result) ) {
                        $this->skin->error($result);
                $this->skin->set_result($result);
                if ( is_wp_error($result) ) {
                        $this->skin->error($result);
@@ -329,15 +688,31 @@ class WP_Upgrader {
                        //Install Succeeded
                        $this->skin->feedback('process_success');
                }
                        //Install Succeeded
                        $this->skin->feedback('process_success');
                }
+
                $this->skin->after();
 
                $this->skin->after();
 
-               if ( !$is_multi )
+               if ( ! $options['is_multi'] ) {
+
+                       /** This action is documented in wp-admin/includes/class-wp-upgrader.php */
+                       do_action( 'upgrader_process_complete', $this, $options['hook_extra'] );
                        $this->skin->footer();
                        $this->skin->footer();
+               }
 
                return $result;
        }
 
 
                return $result;
        }
 
-       function maintenance_mode($enable = false) {
+       /**
+        * Toggle maintenance mode for the site.
+        *
+        * Creates/deletes the maintenance file to enable/disable maintenance mode.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param bool $enable True to enable maintenance mode, false to disable.
+        */
+       public function maintenance_mode( $enable = false ) {
                global $wp_filesystem;
                $file = $wp_filesystem->abspath() . '.maintenance';
                if ( $enable ) {
                global $wp_filesystem;
                $file = $wp_filesystem->abspath() . '.maintenance';
                if ( $enable ) {
@@ -346,7 +721,7 @@ class WP_Upgrader {
                        $maintenance_string = '<?php $upgrading = ' . time() . '; ?>';
                        $wp_filesystem->delete($file);
                        $wp_filesystem->put_contents($file, $maintenance_string, FS_CHMOD_FILE);
                        $maintenance_string = '<?php $upgrading = ' . time() . '; ?>';
                        $wp_filesystem->delete($file);
                        $wp_filesystem->put_contents($file, $maintenance_string, FS_CHMOD_FILE);
-               } else if ( !$enable && $wp_filesystem->exists($file) ) {
+               } elseif ( ! $enable && $wp_filesystem->exists( $file ) ) {
                        $this->skin->feedback('maintenance_end');
                        $wp_filesystem->delete($file);
                }
                        $this->skin->feedback('maintenance_end');
                        $wp_filesystem->delete($file);
                }
@@ -357,19 +732,35 @@ class WP_Upgrader {
 /**
  * Plugin Upgrader class for WordPress Plugins, It is designed to upgrade/install plugins from a local zip, remote zip URL, or uploaded zip file.
  *
 /**
  * Plugin Upgrader class for WordPress Plugins, It is designed to upgrade/install plugins from a local zip, remote zip URL, or uploaded zip file.
  *
- * @TODO More Detailed docs, for methods as well.
- *
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 class Plugin_Upgrader extends WP_Upgrader {
 
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 class Plugin_Upgrader extends WP_Upgrader {
 
-       var $result;
-       var $bulk = false;
-       var $show_before = '';
-
-       function upgrade_strings() {
+       /**
+        * Plugin upgrade result.
+        *
+        * @since 2.8.0
+        * @var array|WP_Error $result
+        * @see WP_Upgrader::$result
+        */
+       public $result;
+
+       /**
+        * Whether a bulk upgrade/install is being performed.
+        *
+        * @since 2.9.0
+        * @var bool $bulk
+        */
+       public $bulk = false;
+
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 2.8.0
+        */
+       public function upgrade_strings() {
                $this->strings['up_to_date'] = __('The plugin is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
                $this->strings['up_to_date'] = __('The plugin is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
@@ -378,45 +769,95 @@ class Plugin_Upgrader extends WP_Upgrader {
                $this->strings['remove_old_failed'] = __('Could not remove the old plugin.');
                $this->strings['process_failed'] = __('Plugin update failed.');
                $this->strings['process_success'] = __('Plugin updated successfully.');
                $this->strings['remove_old_failed'] = __('Could not remove the old plugin.');
                $this->strings['process_failed'] = __('Plugin update failed.');
                $this->strings['process_success'] = __('Plugin updated successfully.');
+               $this->strings['process_bulk_success'] = __('Plugins updated successfully.');
        }
 
        }
 
-       function install_strings() {
+       /**
+        * Initialize the install strings.
+        *
+        * @since 2.8.0
+        */
+       public function install_strings() {
                $this->strings['no_package'] = __('Install package not available.');
                $this->strings['downloading_package'] = __('Downloading install package from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the package&#8230;');
                $this->strings['installing_package'] = __('Installing the plugin&#8230;');
                $this->strings['no_package'] = __('Install package not available.');
                $this->strings['downloading_package'] = __('Downloading install package from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the package&#8230;');
                $this->strings['installing_package'] = __('Installing the plugin&#8230;');
+               $this->strings['no_files'] = __('The plugin contains no files.');
                $this->strings['process_failed'] = __('Plugin install failed.');
                $this->strings['process_success'] = __('Plugin installed successfully.');
        }
 
                $this->strings['process_failed'] = __('Plugin install failed.');
                $this->strings['process_success'] = __('Plugin installed successfully.');
        }
 
-       function install($package) {
+       /**
+        * Install a plugin package.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the plugin update cache optional.
+        *
+        * @param string $package The full local path or URI of the package.
+        * @param array  $args {
+        *     Optional. Other arguments for installing a plugin package. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the plugin updates cache if successful.
+        *                                    Default true.
+        * }
+        *
+        * @return bool|WP_Error True if the install was successful, false or a WP_Error otherwise.
+        */
+       public function install( $package, $args = array() ) {
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->install_strings();
 
 
                $this->init();
                $this->install_strings();
 
-               add_filter('upgrader_source_selection', array(&$this, 'check_package') );
-
-               $this->run(array(
-                                       'package' => $package,
-                                       'destination' => WP_PLUGIN_DIR,
-                                       'clear_destination' => false, //Do not overwrite files.
-                                       'clear_working' => true,
-                                       'hook_extra' => array()
-                                       ));
+               add_filter('upgrader_source_selection', array($this, 'check_package') );
+
+               $this->run( array(
+                       'package' => $package,
+                       'destination' => WP_PLUGIN_DIR,
+                       'clear_destination' => false, // Do not overwrite files.
+                       'clear_working' => true,
+                       'hook_extra' => array(
+                               'type' => 'plugin',
+                               'action' => 'install',
+                       )
+               ) );
 
 
-               remove_filter('upgrader_source_selection', array(&$this, 'check_package') );
+               remove_filter('upgrader_source_selection', array($this, 'check_package') );
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
                // Force refresh of plugin update information
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
                // Force refresh of plugin update information
-               delete_site_transient('update_plugins');
-               wp_cache_delete( 'plugins', 'plugins' );
+               wp_clean_plugins_cache( $parsed_args['clear_update_cache'] );
 
                return true;
        }
 
 
                return true;
        }
 
-       function upgrade($plugin) {
+       /**
+        * Upgrade a plugin.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the plugin update cache optional.
+        *
+        * @param string $plugin The basename path to the main plugin file.
+        * @param array  $args {
+        *     Optional. Other arguments for upgrading a plugin package. Defualt empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the plugin updates cache if successful.
+        *                                    Default true.
+        * }
+        * @return bool|WP_Error True if the upgrade was successful, false or a {@see WP_Error} object otherwise.
+        */
+       public function upgrade( $plugin, $args = array() ) {
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->upgrade_strings();
 
                $this->init();
                $this->upgrade_strings();
@@ -433,33 +874,57 @@ class Plugin_Upgrader extends WP_Upgrader {
                // Get the URL to the zip file
                $r = $current->response[ $plugin ];
 
                // Get the URL to the zip file
                $r = $current->response[ $plugin ];
 
-               add_filter('upgrader_pre_install', array(&$this, 'deactivate_plugin_before_upgrade'), 10, 2);
-               add_filter('upgrader_clear_destination', array(&$this, 'delete_old_plugin'), 10, 4);
-               //'source_selection' => array(&$this, 'source_selection'), //there's a trac ticket to move up the directory for zip's which are made a bit differently, useful for non-.org plugins.
-
-               $this->run(array(
-                                       'package' => $r->package,
-                                       'destination' => WP_PLUGIN_DIR,
-                                       'clear_destination' => true,
-                                       'clear_working' => true,
-                                       'hook_extra' => array(
-                                                               'plugin' => $plugin
-                                       )
-                               ));
+               add_filter('upgrader_pre_install', array($this, 'deactivate_plugin_before_upgrade'), 10, 2);
+               add_filter('upgrader_clear_destination', array($this, 'delete_old_plugin'), 10, 4);
+               //'source_selection' => array($this, 'source_selection'), //there's a trac ticket to move up the directory for zip's which are made a bit differently, useful for non-.org plugins.
+
+               $this->run( array(
+                       'package' => $r->package,
+                       'destination' => WP_PLUGIN_DIR,
+                       'clear_destination' => true,
+                       'clear_working' => true,
+                       'hook_extra' => array(
+                               'plugin' => $plugin,
+                               'type' => 'plugin',
+                               'action' => 'update',
+                       ),
+               ) );
 
                // Cleanup our hooks, in case something else does a upgrade on this connection.
 
                // Cleanup our hooks, in case something else does a upgrade on this connection.
-               remove_filter('upgrader_pre_install', array(&$this, 'deactivate_plugin_before_upgrade'));
-               remove_filter('upgrader_clear_destination', array(&$this, 'delete_old_plugin'));
+               remove_filter('upgrader_pre_install', array($this, 'deactivate_plugin_before_upgrade'));
+               remove_filter('upgrader_clear_destination', array($this, 'delete_old_plugin'));
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
                // Force refresh of plugin update information
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
                // Force refresh of plugin update information
-               delete_site_transient('update_plugins');
-               wp_cache_delete( 'plugins', 'plugins' );
+               wp_clean_plugins_cache( $parsed_args['clear_update_cache'] );
+
+               return true;
        }
 
        }
 
-       function bulk_upgrade($plugins) {
+       /**
+        * Bulk upgrade several plugins at once.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the plugin update cache optional.
+        *
+        * @param array $plugins Array of the basename paths of the plugins' main files.
+        * @param array $args {
+        *     Optional. Other arguments for upgrading several plugins at once. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the plugin updates cache if successful.
+        *                                    Default true.
+        * }
+        *
+        * @return array|false An array of results indexed by plugin file, or false if unable to connect to the filesystem.
+        */
+       public function bulk_upgrade( $plugins, $args = array() ) {
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->bulk = true;
 
                $this->init();
                $this->bulk = true;
@@ -467,7 +932,7 @@ class Plugin_Upgrader extends WP_Upgrader {
 
                $current = get_site_transient( 'update_plugins' );
 
 
                $current = get_site_transient( 'update_plugins' );
 
-               add_filter('upgrader_clear_destination', array(&$this, 'delete_old_plugin'), 10, 4);
+               add_filter('upgrader_clear_destination', array($this, 'delete_old_plugin'), 10, 4);
 
                $this->skin->header();
 
 
                $this->skin->header();
 
@@ -480,10 +945,13 @@ class Plugin_Upgrader extends WP_Upgrader {
 
                $this->skin->bulk_header();
 
 
                $this->skin->bulk_header();
 
-               // Only start maintenance mode if running in Multisite OR the plugin is in use
-               $maintenance = is_multisite(); // @TODO: This should only kick in for individual sites if at all possible.
+               // Only start maintenance mode if:
+               // - running Multisite and there are one or more plugins specified, OR
+               // - a plugin with an update available is currently active.
+               // @TODO: For multisite, maintenance mode should only kick in for individual sites if at all possible.
+               $maintenance = ( is_multisite() && ! empty( $plugins ) );
                foreach ( $plugins as $plugin )
                foreach ( $plugins as $plugin )
-                       $maintenance = $maintenance || (is_plugin_active($plugin) && isset($current->response[ $plugin ]) ); // Only activate Maintenance mode if a plugin is active AND has an update available
+                       $maintenance = $maintenance || ( is_plugin_active( $plugin ) && isset( $current->response[ $plugin] ) );
                if ( $maintenance )
                        $this->maintenance_mode(true);
 
                if ( $maintenance )
                        $this->maintenance_mode(true);
 
@@ -496,7 +964,7 @@ class Plugin_Upgrader extends WP_Upgrader {
                        $this->skin->plugin_info = get_plugin_data( WP_PLUGIN_DIR . '/' . $plugin, false, true);
 
                        if ( !isset( $current->response[ $plugin ] ) ) {
                        $this->skin->plugin_info = get_plugin_data( WP_PLUGIN_DIR . '/' . $plugin, false, true);
 
                        if ( !isset( $current->response[ $plugin ] ) ) {
-                               $this->skin->set_result(true);
+                               $this->skin->set_result('up_to_date');
                                $this->skin->before();
                                $this->skin->feedback('up_to_date');
                                $this->skin->after();
                                $this->skin->before();
                                $this->skin->feedback('up_to_date');
                                $this->skin->after();
@@ -509,16 +977,16 @@ class Plugin_Upgrader extends WP_Upgrader {
 
                        $this->skin->plugin_active = is_plugin_active($plugin);
 
 
                        $this->skin->plugin_active = is_plugin_active($plugin);
 
-                       $result = $this->run(array(
-                                               'package' => $r->package,
-                                               'destination' => WP_PLUGIN_DIR,
-                                               'clear_destination' => true,
-                                               'clear_working' => true,
-                                               'is_multi' => true,
-                                               'hook_extra' => array(
-                                                                       'plugin' => $plugin
-                                               )
-                                       ));
+                       $result = $this->run( array(
+                               'package' => $r->package,
+                               'destination' => WP_PLUGIN_DIR,
+                               'clear_destination' => true,
+                               'clear_working' => true,
+                               'is_multi' => true,
+                               'hook_extra' => array(
+                                       'plugin' => $plugin
+                               )
+                       );
 
                        $results[$plugin] = $this->result;
 
 
                        $results[$plugin] = $this->result;
 
@@ -529,48 +997,94 @@ class Plugin_Upgrader extends WP_Upgrader {
 
                $this->maintenance_mode(false);
 
 
                $this->maintenance_mode(false);
 
+               /**
+                * Fires when the bulk upgrader process is complete.
+                *
+                * @since 3.6.0
+                *
+                * @param Plugin_Upgrader $this Plugin_Upgrader instance. In other contexts, $this, might
+                *                              be a Theme_Upgrader or Core_Upgrade instance.
+                * @param array           $data {
+                *     Array of bulk item update data.
+                *
+                *     @type string $action   Type of action. Default 'update'.
+                *     @type string $type     Type of update process. Accepts 'plugin', 'theme', or 'core'.
+                *     @type bool   $bulk     Whether the update process is a bulk update. Default true.
+                *     @type array  $packages Array of plugin, theme, or core packages to update.
+                * }
+                */
+               do_action( 'upgrader_process_complete', $this, array(
+                       'action' => 'update',
+                       'type' => 'plugin',
+                       'bulk' => true,
+                       'plugins' => $plugins,
+               ) );
+
                $this->skin->bulk_footer();
 
                $this->skin->footer();
 
                // Cleanup our hooks, in case something else does a upgrade on this connection.
                $this->skin->bulk_footer();
 
                $this->skin->footer();
 
                // Cleanup our hooks, in case something else does a upgrade on this connection.
-               remove_filter('upgrader_clear_destination', array(&$this, 'delete_old_plugin'));
+               remove_filter('upgrader_clear_destination', array($this, 'delete_old_plugin'));
 
                // Force refresh of plugin update information
 
                // Force refresh of plugin update information
-               delete_site_transient('update_plugins');
-               wp_cache_delete( 'plugins', 'plugins' );
+               wp_clean_plugins_cache( $parsed_args['clear_update_cache'] );
 
                return $results;
        }
 
 
                return $results;
        }
 
-       function check_package($source) {
+       /**
+        * Check a source package to be sure it contains a plugin.
+        *
+        * This function is added to the {@see 'upgrader_source_selection'} filter by
+        * {@see Plugin_Upgrader::install()}.
+        *
+        * @since 3.3.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $source The path to the downloaded package source.
+        * @return string|WP_Error The source as passed, or a {@see WP_Error} object if no plugins were found.
+        */
+       public function check_package($source) {
                global $wp_filesystem;
 
                if ( is_wp_error($source) )
                        return $source;
 
                $working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit(WP_CONTENT_DIR), $source);
                global $wp_filesystem;
 
                if ( is_wp_error($source) )
                        return $source;
 
                $working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit(WP_CONTENT_DIR), $source);
-               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, lets not prevent installation.
+               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, let's not prevent installation.
                        return $source;
 
                // Check the folder contains at least 1 valid plugin.
                $plugins_found = false;
                        return $source;
 
                // Check the folder contains at least 1 valid plugin.
                $plugins_found = false;
-               foreach ( glob( $working_directory . '*.php' ) as $file ) {
-                       $info = get_plugin_data($file, false, false);
-                       if ( !empty( $info['Name'] ) ) {
-                               $plugins_found = true;
-                               break;
+               $files = glob( $working_directory . '*.php' );
+               if ( $files ) {
+                       foreach ( $files as $file ) {
+                               $info = get_plugin_data( $file, false, false );
+                               if ( ! empty( $info['Name'] ) ) {
+                                       $plugins_found = true;
+                                       break;
+                               }
                        }
                }
 
                if ( ! $plugins_found )
                        }
                }
 
                if ( ! $plugins_found )
-                       return new WP_Error( 'incompatible_archive', $this->strings['incompatible_archive'], __('No valid plugins were found.') );
+                       return new WP_Error( 'incompatible_archive_no_plugins', $this->strings['incompatible_archive'], __( 'No valid plugins were found.' ) );
 
                return $source;
        }
 
 
                return $source;
        }
 
-       //return plugin info.
-       function plugin_info() {
+       /**
+        * Retrieve the path to the file that contains the plugin info.
+        *
+        * This isn't used internally in the class, but is called by the skins.
+        *
+        * @since 2.8.0
+        *
+        * @return string|false The full path to the main plugin file, or false.
+        */
+       public function plugin_info() {
                if ( ! is_array($this->result) )
                        return false;
                if ( empty($this->result['destination_name']) )
                if ( ! is_array($this->result) )
                        return false;
                if ( empty($this->result['destination_name']) )
@@ -585,12 +1099,27 @@ class Plugin_Upgrader extends WP_Upgrader {
                return $this->result['destination_name'] . '/' . $pluginfiles[0];
        }
 
                return $this->result['destination_name'] . '/' . $pluginfiles[0];
        }
 
-       //Hooked to pre_install
-       function deactivate_plugin_before_upgrade($return, $plugin) {
+       /**
+        * Deactivates a plugin before it is upgraded.
+        *
+        * Hooked to the {@see 'upgrader_pre_install'} filter by {@see Plugin_Upgrader::upgrade()}.
+        *
+        * @since 2.8.0
+        * @since 4.1.0 Added a return value.
+        *
+        * @param bool|WP_Error  $return Upgrade offer return.
+        * @param array          $plugin Plugin package arguments.
+        * @return bool|WP_Error The passed in $return param or {@see WP_Error}.
+        */
+       public function deactivate_plugin_before_upgrade($return, $plugin) {
 
                if ( is_wp_error($return) ) //Bypass.
                        return $return;
 
 
                if ( is_wp_error($return) ) //Bypass.
                        return $return;
 
+               // When in cron (background updates) don't deactivate the plugin, as we require a browser to reactivate it
+               if ( defined( 'DOING_CRON' ) && DOING_CRON )
+                       return $return;
+
                $plugin = isset($plugin['plugin']) ? $plugin['plugin'] : '';
                if ( empty($plugin) )
                        return new WP_Error('bad_request', $this->strings['bad_request']);
                $plugin = isset($plugin['plugin']) ? $plugin['plugin'] : '';
                if ( empty($plugin) )
                        return new WP_Error('bad_request', $this->strings['bad_request']);
@@ -599,10 +1128,27 @@ class Plugin_Upgrader extends WP_Upgrader {
                        //Deactivate the plugin silently, Prevent deactivation hooks from running.
                        deactivate_plugins($plugin, true);
                }
                        //Deactivate the plugin silently, Prevent deactivation hooks from running.
                        deactivate_plugins($plugin, true);
                }
+
+               return $return;
        }
 
        }
 
-       //Hooked to upgrade_clear_destination
-       function delete_old_plugin($removed, $local_destination, $remote_destination, $plugin) {
+       /**
+        * Delete the old plugin during an upgrade.
+        *
+        * Hooked to the {@see 'upgrader_clear_destination'} filter by
+        * {@see Plugin_Upgrader::upgrade()} and {@see Plugin_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+     *
+        * @param bool|WP_Error $removed
+        * @param string        $local_destination
+        * @param string        $remote_destination
+        * @param array         $plugin
+        * @return WP_Error|bool
+        */
+       public function delete_old_plugin($removed, $local_destination, $remote_destination, $plugin) {
                global $wp_filesystem;
 
                if ( is_wp_error($removed) )
                global $wp_filesystem;
 
                if ( is_wp_error($removed) )
@@ -615,11 +1161,11 @@ class Plugin_Upgrader extends WP_Upgrader {
                $plugins_dir = $wp_filesystem->wp_plugins_dir();
                $this_plugin_dir = trailingslashit( dirname($plugins_dir . $plugin) );
 
                $plugins_dir = $wp_filesystem->wp_plugins_dir();
                $this_plugin_dir = trailingslashit( dirname($plugins_dir . $plugin) );
 
-               if ( ! $wp_filesystem->exists($this_plugin_dir) ) //If its already vanished.
+               if ( ! $wp_filesystem->exists($this_plugin_dir) ) //If it's already vanished.
                        return $removed;
 
                // If plugin is in its own directory, recursively delete the directory.
                        return $removed;
 
                // If plugin is in its own directory, recursively delete the directory.
-               if ( strpos($plugin, '/') && $this_plugin_dir != $plugins_dir ) //base check on if plugin includes directory separator AND that its not the root plugin folder
+               if ( strpos($plugin, '/') && $this_plugin_dir != $plugins_dir ) //base check on if plugin includes directory separator AND that it's not the root plugin folder
                        $deleted = $wp_filesystem->delete($this_plugin_dir, true);
                else
                        $deleted = $wp_filesystem->delete($plugins_dir . $plugin);
                        $deleted = $wp_filesystem->delete($this_plugin_dir, true);
                else
                        $deleted = $wp_filesystem->delete($plugins_dir . $plugin);
@@ -634,18 +1180,35 @@ class Plugin_Upgrader extends WP_Upgrader {
 /**
  * Theme Upgrader class for WordPress Themes, It is designed to upgrade/install themes from a local zip, remote zip URL, or uploaded zip file.
  *
 /**
  * Theme Upgrader class for WordPress Themes, It is designed to upgrade/install themes from a local zip, remote zip URL, or uploaded zip file.
  *
- * @TODO More Detailed docs, for methods as well.
- *
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 class Theme_Upgrader extends WP_Upgrader {
 
  * @package WordPress
  * @subpackage Upgrader
  * @since 2.8.0
  */
 class Theme_Upgrader extends WP_Upgrader {
 
-       var $result;
-       var $bulk = false;
-
-       function upgrade_strings() {
+       /**
+        * Result of the theme upgrade offer.
+        *
+        * @since 2.8.0
+        * @var array|WP_Erorr $result
+        * @see WP_Upgrader::$result
+        */
+       public $result;
+
+       /**
+        * Whether multiple plugins are being upgraded/installed in bulk.
+        *
+        * @since 2.9.0
+        * @var bool $bulk
+        */
+       public $bulk = false;
+
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 2.8.0
+        */
+       public function upgrade_strings() {
                $this->strings['up_to_date'] = __('The theme is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
                $this->strings['up_to_date'] = __('The theme is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
@@ -656,11 +1219,17 @@ class Theme_Upgrader extends WP_Upgrader {
                $this->strings['process_success'] = __('Theme updated successfully.');
        }
 
                $this->strings['process_success'] = __('Theme updated successfully.');
        }
 
-       function install_strings() {
+       /**
+        * Initialize the install strings.
+        *
+        * @since 2.8.0
+        */
+       public function install_strings() {
                $this->strings['no_package'] = __('Install package not available.');
                $this->strings['downloading_package'] = __('Downloading install package from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the package&#8230;');
                $this->strings['installing_package'] = __('Installing the theme&#8230;');
                $this->strings['no_package'] = __('Install package not available.');
                $this->strings['downloading_package'] = __('Downloading install package from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the package&#8230;');
                $this->strings['installing_package'] = __('Installing the theme&#8230;');
+               $this->strings['no_files'] = __('The theme contains no files.');
                $this->strings['process_failed'] = __('Theme install failed.');
                $this->strings['process_success'] = __('Theme installed successfully.');
                /* translators: 1: theme name, 2: version */
                $this->strings['process_failed'] = __('Theme install failed.');
                $this->strings['process_success'] = __('Theme installed successfully.');
                /* translators: 1: theme name, 2: version */
@@ -675,7 +1244,19 @@ class Theme_Upgrader extends WP_Upgrader {
                $this->strings['parent_theme_not_found'] = __('<strong>The parent theme could not be found.</strong> You will need to install the parent theme, <strong>%s</strong>, before you can use this child theme.');
        }
 
                $this->strings['parent_theme_not_found'] = __('<strong>The parent theme could not be found.</strong> You will need to install the parent theme, <strong>%s</strong>, before you can use this child theme.');
        }
 
-       function check_parent_theme_filter($install_result, $hook_extra, $child_result) {
+       /**
+        * Check if a child theme is being installed and we need to install its parent.
+        *
+        * Hooked to the {@see 'upgrader_post_install'} filter by {@see Theme_Upgrader::install()}.
+        *
+        * @since 3.4.0
+        *
+        * @param bool  $install_result
+        * @param array $hook_extra
+        * @param array $child_result
+        * @return type
+        */
+       public function check_parent_theme_filter( $install_result, $hook_extra, $child_result ) {
                // Check to see if we need to install a parent theme
                $theme_info = $this->theme_info();
 
                // Check to see if we need to install a parent theme
                $theme_info = $this->theme_info();
 
@@ -690,13 +1271,13 @@ class Theme_Upgrader extends WP_Upgrader {
                        return $install_result;
                }
 
                        return $install_result;
                }
 
-               // We don't have the parent theme, lets install it
+               // We don't have the parent theme, let's install it.
                $api = themes_api('theme_information', array('slug' => $theme_info->get('Template'), 'fields' => array('sections' => false, 'tags' => false) ) ); //Save on a bit of bandwidth.
 
                if ( ! $api || is_wp_error($api) ) {
                        $this->skin->feedback( 'parent_theme_not_found', $theme_info->get('Template') );
                        // Don't show activate or preview actions after install
                $api = themes_api('theme_information', array('slug' => $theme_info->get('Template'), 'fields' => array('sections' => false, 'tags' => false) ) ); //Save on a bit of bandwidth.
 
                if ( ! $api || is_wp_error($api) ) {
                        $this->skin->feedback( 'parent_theme_not_found', $theme_info->get('Template') );
                        // Don't show activate or preview actions after install
-                       add_filter('install_theme_complete_actions', array(&$this, 'hide_activate_preview_actions') );
+                       add_filter('install_theme_complete_actions', array($this, 'hide_activate_preview_actions') );
                        return $install_result;
                }
 
                        return $install_result;
                }
 
@@ -715,13 +1296,13 @@ class Theme_Upgrader extends WP_Upgrader {
                // Install the parent theme
                $parent_result = $this->run( array(
                        'package' => $api->download_link,
                // Install the parent theme
                $parent_result = $this->run( array(
                        'package' => $api->download_link,
-                       'destination' => WP_CONTENT_DIR . '/themes',
+                       'destination' => get_theme_root(),
                        'clear_destination' => false, //Do not overwrite files.
                        'clear_working' => true
                ) );
 
                if ( is_wp_error($parent_result) )
                        'clear_destination' => false, //Do not overwrite files.
                        'clear_working' => true
                ) );
 
                if ( is_wp_error($parent_result) )
-                       add_filter('install_theme_complete_actions', array(&$this, 'hide_activate_preview_actions') );
+                       add_filter('install_theme_complete_actions', array($this, 'hide_activate_preview_actions') );
 
                // Start cleaning up after the parents installation
                remove_filter('install_theme_complete_actions', '__return_false', 999);
 
                // Start cleaning up after the parents installation
                remove_filter('install_theme_complete_actions', '__return_false', 999);
@@ -734,41 +1315,96 @@ class Theme_Upgrader extends WP_Upgrader {
                return $install_result;
        }
 
                return $install_result;
        }
 
-       function hide_activate_preview_actions($actions) {
+       /**
+        * Don't display the activate and preview actions to the user.
+        *
+        * Hooked to the {@see 'install_theme_complete_actions'} filter by
+        * {@see Theme_Upgrader::check_parent_theme_filter()} when installing
+        * a child theme and installing the parent theme fails.
+        *
+        * @since 3.4.0
+        *
+        * @param array $actions Preview actions.
+        * @return array
+        */
+       public function hide_activate_preview_actions( $actions ) {
                unset($actions['activate'], $actions['preview']);
                return $actions;
        }
 
                unset($actions['activate'], $actions['preview']);
                return $actions;
        }
 
-       function install($package) {
+       /**
+        * Install a theme package.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
+        *
+        * @param string $package The full local path or URI of the package.
+        * @param array  $args {
+        *     Optional. Other arguments for installing a theme package. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the updates cache if successful.
+        *                                    Default true.
+        * }
+        *
+        * @return bool|WP_Error True if the install was successful, false or a {@see WP_Error} object otherwise.
+        */
+       public function install( $package, $args = array() ) {
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->install_strings();
 
 
                $this->init();
                $this->install_strings();
 
-               add_filter('upgrader_source_selection', array(&$this, 'check_package') );
-               add_filter('upgrader_post_install', array(&$this, 'check_parent_theme_filter'), 10, 3);
+               add_filter('upgrader_source_selection', array($this, 'check_package') );
+               add_filter('upgrader_post_install', array($this, 'check_parent_theme_filter'), 10, 3);
 
 
-               $options = array(
-                                               'package' => $package,
-                                               'destination' => WP_CONTENT_DIR . '/themes',
-                                               'clear_destination' => false, //Do not overwrite files.
-                                               'clear_working' => true
-                                               );
-
-               $this->run($options);
+               $this->run( array(
+                       'package' => $package,
+                       'destination' => get_theme_root(),
+                       'clear_destination' => false, //Do not overwrite files.
+                       'clear_working' => true,
+                       'hook_extra' => array(
+                               'type' => 'theme',
+                               'action' => 'install',
+                       ),
+               ) );
 
 
-               remove_filter('upgrader_source_selection', array(&$this, 'check_package') );
-               remove_filter('upgrader_post_install', array(&$this, 'check_parent_theme_filter'), 10, 3);
+               remove_filter('upgrader_source_selection', array($this, 'check_package') );
+               remove_filter('upgrader_post_install', array($this, 'check_parent_theme_filter'));
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
-               // Force refresh of theme update information
-               wp_clean_themes_cache();
+               // Refresh the Theme Update information
+               wp_clean_themes_cache( $parsed_args['clear_update_cache'] );
 
                return true;
        }
 
 
                return true;
        }
 
-       function upgrade($theme) {
+       /**
+        * Upgrade a theme.
+        *
+        * @since 2.8.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
+        *
+        * @param string $theme The theme slug.
+        * @param array  $args {
+        *     Optional. Other arguments for upgrading a theme. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the update cache if successful.
+        *                                    Default true.
+        * }
+        * @return bool|WP_Error True if the upgrade was successful, false or a {@see WP_Error} object otherwise.
+        */
+       public function upgrade( $theme, $args = array() ) {
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->upgrade_strings();
 
                $this->init();
                $this->upgrade_strings();
@@ -778,43 +1414,62 @@ class Theme_Upgrader extends WP_Upgrader {
                if ( !isset( $current->response[ $theme ] ) ) {
                        $this->skin->before();
                        $this->skin->set_result(false);
                if ( !isset( $current->response[ $theme ] ) ) {
                        $this->skin->before();
                        $this->skin->set_result(false);
-                       $this->skin->error('up_to_date');
+                       $this->skin->error( 'up_to_date' );
                        $this->skin->after();
                        return false;
                }
 
                $r = $current->response[ $theme ];
 
                        $this->skin->after();
                        return false;
                }
 
                $r = $current->response[ $theme ];
 
-               add_filter('upgrader_pre_install', array(&$this, 'current_before'), 10, 2);
-               add_filter('upgrader_post_install', array(&$this, 'current_after'), 10, 2);
-               add_filter('upgrader_clear_destination', array(&$this, 'delete_old_theme'), 10, 4);
-
-               $options = array(
-                                               'package' => $r['package'],
-                                               'destination' => WP_CONTENT_DIR . '/themes',
-                                               'clear_destination' => true,
-                                               'clear_working' => true,
-                                               'hook_extra' => array(
-                                                                                       'theme' => $theme
-                                                                                       )
-                                               );
-
-               $this->run($options);
+               add_filter('upgrader_pre_install', array($this, 'current_before'), 10, 2);
+               add_filter('upgrader_post_install', array($this, 'current_after'), 10, 2);
+               add_filter('upgrader_clear_destination', array($this, 'delete_old_theme'), 10, 4);
+
+               $this->run( array(
+                       'package' => $r['package'],
+                       'destination' => get_theme_root( $theme ),
+                       'clear_destination' => true,
+                       'clear_working' => true,
+                       'hook_extra' => array(
+                               'theme' => $theme,
+                               'type' => 'theme',
+                               'action' => 'update',
+                       ),
+               );
 
 
-               remove_filter('upgrader_pre_install', array(&$this, 'current_before'), 10, 2);
-               remove_filter('upgrader_post_install', array(&$this, 'current_after'), 10, 2);
-               remove_filter('upgrader_clear_destination', array(&$this, 'delete_old_theme'), 10, 4);
+               remove_filter('upgrader_pre_install', array($this, 'current_before'));
+               remove_filter('upgrader_post_install', array($this, 'current_after'));
+               remove_filter('upgrader_clear_destination', array($this, 'delete_old_theme'));
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
 
                if ( ! $this->result || is_wp_error($this->result) )
                        return $this->result;
 
-               // Force refresh of theme update information
-               wp_clean_themes_cache();
+               wp_clean_themes_cache( $parsed_args['clear_update_cache'] );
 
                return true;
        }
 
 
                return true;
        }
 
-       function bulk_upgrade($themes) {
+       /**
+        * Upgrade several themes at once.
+        *
+        * @since 3.0.0
+        * @since 3.7.0 The `$args` parameter was added, making clearing the update cache optional.
+        *
+        * @param array $themes The theme slugs.
+        * @param array $args {
+        *     Optional. Other arguments for upgrading several themes at once. Default empty array.
+        *
+        *     @type bool $clear_update_cache Whether to clear the update cache if successful.
+        *                                    Default true.
+        * }
+        * @return array[]|false An array of results, or false if unable to connect to the filesystem.
+        */
+       public function bulk_upgrade( $themes, $args = array() ) {
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->bulk = true;
 
                $this->init();
                $this->bulk = true;
@@ -822,9 +1477,9 @@ class Theme_Upgrader extends WP_Upgrader {
 
                $current = get_site_transient( 'update_themes' );
 
 
                $current = get_site_transient( 'update_themes' );
 
-               add_filter('upgrader_pre_install', array(&$this, 'current_before'), 10, 2);
-               add_filter('upgrader_post_install', array(&$this, 'current_after'), 10, 2);
-               add_filter('upgrader_clear_destination', array(&$this, 'delete_old_theme'), 10, 4);
+               add_filter('upgrader_pre_install', array($this, 'current_before'), 10, 2);
+               add_filter('upgrader_post_install', array($this, 'current_after'), 10, 2);
+               add_filter('upgrader_clear_destination', array($this, 'delete_old_theme'), 10, 4);
 
                $this->skin->header();
 
 
                $this->skin->header();
 
@@ -837,8 +1492,11 @@ class Theme_Upgrader extends WP_Upgrader {
 
                $this->skin->bulk_header();
 
 
                $this->skin->bulk_header();
 
-               // Only start maintenance mode if running in Multisite OR the theme is in use
-               $maintenance = is_multisite(); // @TODO: This should only kick in for individual sites if at all possible.
+               // Only start maintenance mode if:
+               // - running Multisite and there are one or more themes specified, OR
+               // - a theme with an update available is currently in use.
+               // @TODO: For multisite, maintenance mode should only kick in for individual sites if at all possible.
+               $maintenance = ( is_multisite() && ! empty( $themes ) );
                foreach ( $themes as $theme )
                        $maintenance = $maintenance || $theme == get_stylesheet() || $theme == get_template();
                if ( $maintenance )
                foreach ( $themes as $theme )
                        $maintenance = $maintenance || $theme == get_stylesheet() || $theme == get_template();
                if ( $maintenance )
@@ -856,7 +1514,7 @@ class Theme_Upgrader extends WP_Upgrader {
                        if ( !isset( $current->response[ $theme ] ) ) {
                                $this->skin->set_result(true);
                                $this->skin->before();
                        if ( !isset( $current->response[ $theme ] ) ) {
                                $this->skin->set_result(true);
                                $this->skin->before();
-                               $this->skin->feedback('up_to_date');
+                               $this->skin->feedback( 'up_to_date' );
                                $this->skin->after();
                                $results[$theme] = true;
                                continue;
                                $this->skin->after();
                                $results[$theme] = true;
                                continue;
@@ -865,17 +1523,16 @@ class Theme_Upgrader extends WP_Upgrader {
                        // Get the URL to the zip file
                        $r = $current->response[ $theme ];
 
                        // Get the URL to the zip file
                        $r = $current->response[ $theme ];
 
-                       $options = array(
-                                                       'package' => $r['package'],
-                                                       'destination' => WP_CONTENT_DIR . '/themes',
-                                                       'clear_destination' => true,
-                                                       'clear_working' => true,
-                                                       'hook_extra' => array(
-                                                                                               'theme' => $theme
-                                                                                               )
-                                                       );
-
-                       $result = $this->run($options);
+                       $result = $this->run( array(
+                               'package' => $r['package'],
+                               'destination' => get_theme_root( $theme ),
+                               'clear_destination' => true,
+                               'clear_working' => true,
+                               'is_multi' => true,
+                               'hook_extra' => array(
+                                       'theme' => $theme
+                               ),
+                       ) );
 
                        $results[$theme] = $this->result;
 
 
                        $results[$theme] = $this->result;
 
@@ -886,22 +1543,44 @@ class Theme_Upgrader extends WP_Upgrader {
 
                $this->maintenance_mode(false);
 
 
                $this->maintenance_mode(false);
 
+               /** This action is documented in wp-admin/includes/class-wp-upgrader.php */
+               do_action( 'upgrader_process_complete', $this, array(
+                       'action' => 'update',
+                       'type' => 'theme',
+                       'bulk' => true,
+                       'themes' => $themes,
+               ) );
+
                $this->skin->bulk_footer();
 
                $this->skin->footer();
 
                // Cleanup our hooks, in case something else does a upgrade on this connection.
                $this->skin->bulk_footer();
 
                $this->skin->footer();
 
                // Cleanup our hooks, in case something else does a upgrade on this connection.
-               remove_filter('upgrader_pre_install', array(&$this, 'current_before'), 10, 2);
-               remove_filter('upgrader_post_install', array(&$this, 'current_after'), 10, 2);
-               remove_filter('upgrader_clear_destination', array(&$this, 'delete_old_theme'), 10, 4);
+               remove_filter('upgrader_pre_install', array($this, 'current_before'));
+               remove_filter('upgrader_post_install', array($this, 'current_after'));
+               remove_filter('upgrader_clear_destination', array($this, 'delete_old_theme'));
 
 
-               // Force refresh of theme update information
-               wp_clean_themes_cache();
+               // Refresh the Theme Update information
+               wp_clean_themes_cache( $parsed_args['clear_update_cache'] );
 
                return $results;
        }
 
 
                return $results;
        }
 
-       function check_package($source) {
+       /**
+        * Check that the package source contains a valid theme.
+        *
+        * Hooked to the {@see 'upgrader_source_selection'} filter by {@see Theme_Upgrader::install()}.
+        * It will return an error if the theme doesn't have style.css or index.php
+        * files.
+        *
+        * @since 3.3.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string $source The full path to the package source.
+        * @return string|WP_Error The source or a WP_Error.
+        */
+       public function check_package( $source ) {
                global $wp_filesystem;
 
                if ( is_wp_error($source) )
                global $wp_filesystem;
 
                if ( is_wp_error($source) )
@@ -909,27 +1588,38 @@ class Theme_Upgrader extends WP_Upgrader {
 
                // Check the folder contains a valid theme
                $working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit(WP_CONTENT_DIR), $source);
 
                // Check the folder contains a valid theme
                $working_directory = str_replace( $wp_filesystem->wp_content_dir(), trailingslashit(WP_CONTENT_DIR), $source);
-               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, lets not prevent installation.
+               if ( ! is_dir($working_directory) ) // Sanity check, if the above fails, let's not prevent installation.
                        return $source;
 
                // A proper archive should have a style.css file in the single subdirectory
                if ( ! file_exists( $working_directory . 'style.css' ) )
                        return $source;
 
                // A proper archive should have a style.css file in the single subdirectory
                if ( ! file_exists( $working_directory . 'style.css' ) )
-                       return new WP_Error( 'incompatible_archive', $this->strings['incompatible_archive'], __('The theme is missing the <code>style.css</code> stylesheet.') );
+                       return new WP_Error( 'incompatible_archive_theme_no_style', $this->strings['incompatible_archive'], __( 'The theme is missing the <code>style.css</code> stylesheet.' ) );
 
                $info = get_file_data( $working_directory . 'style.css', array( 'Name' => 'Theme Name', 'Template' => 'Template' ) );
 
                if ( empty( $info['Name'] ) )
 
                $info = get_file_data( $working_directory . 'style.css', array( 'Name' => 'Theme Name', 'Template' => 'Template' ) );
 
                if ( empty( $info['Name'] ) )
-                       return new WP_Error( 'incompatible_archive', $this->strings['incompatible_archive'], __("The <code>style.css</code> stylesheet doesn't contain a valid theme header.") );
+                       return new WP_Error( 'incompatible_archive_theme_no_name', $this->strings['incompatible_archive'], __( "The <code>style.css</code> stylesheet doesn't contain a valid theme header." ) );
 
                // If it's not a child theme, it must have at least an index.php to be legit.
                if ( empty( $info['Template'] ) && ! file_exists( $working_directory . 'index.php' ) )
 
                // If it's not a child theme, it must have at least an index.php to be legit.
                if ( empty( $info['Template'] ) && ! file_exists( $working_directory . 'index.php' ) )
-                       return new WP_Error( 'incompatible_archive', $this->strings['incompatible_archive'], __('The theme is missing the <code>index.php</code> file.') );
+                       return new WP_Error( 'incompatible_archive_theme_no_index', $this->strings['incompatible_archive'], __( 'The theme is missing the <code>index.php</code> file.' ) );
 
                return $source;
        }
 
 
                return $source;
        }
 
-       function current_before($return, $theme) {
-
+       /**
+        * Turn on maintenance mode before attempting to upgrade the current theme.
+        *
+        * Hooked to the {@see 'upgrader_pre_install'} filter by {@see Theme_Upgrader::upgrade()} and
+        * {@see Theme_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        *
+        * @param bool|WP_Error  $return
+        * @param array          $theme
+        * @return bool|WP_Error
+        */
+       public function current_before($return, $theme) {
                if ( is_wp_error($return) )
                        return $return;
 
                if ( is_wp_error($return) )
                        return $return;
 
@@ -944,7 +1634,19 @@ class Theme_Upgrader extends WP_Upgrader {
                return $return;
        }
 
                return $return;
        }
 
-       function current_after($return, $theme) {
+       /**
+        * Turn off maintenance mode after upgrading the current theme.
+        *
+        * Hooked to the {@see 'upgrader_post_install'} filter by {@see Theme_Upgrader::upgrade()}
+        * and {@see Theme_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        *
+        * @param bool|WP_Error  $return
+        * @param array          $theme
+        * @return bool|WP_Error
+        */
+       public function current_after($return, $theme) {
                if ( is_wp_error($return) )
                        return $return;
 
                if ( is_wp_error($return) )
                        return $return;
 
@@ -966,22 +1668,53 @@ class Theme_Upgrader extends WP_Upgrader {
                return $return;
        }
 
                return $return;
        }
 
-       function delete_old_theme($removed, $local_destination, $remote_destination, $theme) {
+       /**
+        * Delete the old theme during an upgrade.
+        *
+        * Hooked to the {@see 'upgrader_clear_destination'} filter by {@see Theme_Upgrader::upgrade()}
+        * and {@see Theme_Upgrader::bulk_upgrade()}.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param bool   $removed
+        * @param string $local_destination
+        * @param string $remote_destination
+        * @param array  $theme
+        * @return bool
+        */
+       public function delete_old_theme( $removed, $local_destination, $remote_destination, $theme ) {
                global $wp_filesystem;
 
                global $wp_filesystem;
 
-               $theme = isset($theme['theme']) ? $theme['theme'] : '';
+               if ( is_wp_error( $removed ) )
+                       return $removed; // Pass errors through.
 
 
-               if ( is_wp_error($removed) || empty($theme) )
-                       return $removed; //Pass errors through.
+               if ( ! isset( $theme['theme'] ) )
+                       return $removed;
 
 
-               $themes_dir = $wp_filesystem->wp_themes_dir();
-               if ( $wp_filesystem->exists( trailingslashit($themes_dir) . $theme ) )
-                       if ( ! $wp_filesystem->delete( trailingslashit($themes_dir) . $theme, true ) )
+               $theme = $theme['theme'];
+               $themes_dir = trailingslashit( $wp_filesystem->wp_themes_dir( $theme ) );
+               if ( $wp_filesystem->exists( $themes_dir . $theme ) ) {
+                       if ( ! $wp_filesystem->delete( $themes_dir . $theme, true ) )
                                return false;
                                return false;
+               }
+
                return true;
        }
 
                return true;
        }
 
-       function theme_info($theme = null) {
+       /**
+        * Get the WP_Theme object for a theme.
+        *
+        * @since 2.8.0
+        * @since 3.0.0 The `$theme` argument was added.
+        *
+        * @param string $theme The directory name of the theme. This is optional, and if not supplied,
+        *                      the directory name from the last result will be used.
+        * @return WP_Theme|false The theme's info object, or false `$theme` is not supplied
+        *                        and the last result isn't set.
+        */
+       public function theme_info($theme = null) {
 
                if ( empty($theme) ) {
                        if ( !empty($this->result['destination_name']) )
 
                if ( empty($theme) ) {
                        if ( !empty($this->result['destination_name']) )
@@ -989,15 +1722,330 @@ class Theme_Upgrader extends WP_Upgrader {
                        else
                                return false;
                }
                        else
                                return false;
                }
-               return wp_get_theme( $theme, WP_CONTENT_DIR . '/themes/' );
+               return wp_get_theme( $theme );
        }
 
 }
 
 /**
        }
 
 }
 
 /**
- * Core Upgrader class for WordPress. It allows for WordPress to upgrade itself in combination with the wp-admin/includes/update-core.php file
+ * Language pack upgrader, for updating translations of plugins, themes, and core.
  *
  *
- * @TODO More Detailed docs, for methods as well.
+ * @package WordPress
+ * @subpackage Upgrader
+ * @since 3.7.0
+ */
+class Language_Pack_Upgrader extends WP_Upgrader {
+
+       /**
+        * Result of the language pack upgrade.
+        *
+        * @since 3.7.0
+        * @var array|WP_Error $result
+        * @see WP_Upgrader::$result
+        */
+       public $result;
+
+       /**
+        * Whether a bulk upgrade/install is being performed.
+        *
+        * @since 3.7.0
+        * @var bool $bulk
+        */
+       public $bulk = true;
+
+       /**
+        * Asynchronously upgrade language packs after other upgrades have been made.
+        *
+        * Hooked to the {@see 'upgrader_process_complete'} action by default.
+        *
+        * @since 3.7.0
+        *
+        * @static
+        *
+        * @param false|WP_Upgrader $upgrader
+        */
+       public static function async_upgrade( $upgrader = false ) {
+               // Avoid recursion.
+               if ( $upgrader && $upgrader instanceof Language_Pack_Upgrader ) {
+                       return;
+               }
+
+               // Nothing to do?
+               $language_updates = wp_get_translation_updates();
+               if ( ! $language_updates ) {
+                       return;
+               }
+
+               // Avoid messing with VCS installs, at least for now.
+               // Noted: this is not the ideal way to accomplish this.
+               $check_vcs = new WP_Automatic_Updater;
+               if ( $check_vcs->is_vcs_checkout( WP_CONTENT_DIR ) ) {
+                       return;
+               }
+
+               foreach ( $language_updates as $key => $language_update ) {
+                       $update = ! empty( $language_update->autoupdate );
+
+                       /**
+                        * Filter whether to asynchronously update translation for core, a plugin, or a theme.
+                        *
+                        * @since 4.0.0
+                        *
+                        * @param bool   $update          Whether to update.
+                        * @param object $language_update The update offer.
+                        */
+                       $update = apply_filters( 'async_update_translation', $update, $language_update );
+
+                       if ( ! $update ) {
+                               unset( $language_updates[ $key ] );
+                       }
+               }
+
+               if ( empty( $language_updates ) ) {
+                       return;
+               }
+
+               $skin = new Language_Pack_Upgrader_Skin( array(
+                       'skip_header_footer' => true,
+               ) );
+
+               $lp_upgrader = new Language_Pack_Upgrader( $skin );
+               $lp_upgrader->bulk_upgrade( $language_updates );
+       }
+
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 3.7.0
+        */
+       public function upgrade_strings() {
+               $this->strings['starting_upgrade'] = __( 'Some of your translations need updating. Sit tight for a few more seconds while we update them as well.' );
+               $this->strings['up_to_date'] = __( 'The translation is up to date.' ); // We need to silently skip this case
+               $this->strings['no_package'] = __( 'Update package not available.' );
+               $this->strings['downloading_package'] = __( 'Downloading translation from <span class="code">%s</span>&#8230;' );
+               $this->strings['unpack_package'] = __( 'Unpacking the update&#8230;' );
+               $this->strings['process_failed'] = __( 'Translation update failed.' );
+               $this->strings['process_success'] = __( 'Translation updated successfully.' );
+       }
+
+       /**
+        * Upgrade a language pack.
+        *
+        * @since 3.7.0
+        *
+        * @param string|false $update Optional. Whether an update offer is available. Default false.
+        * @param array        $args   Optional. Other optional arguments, see
+        *                             {@see Language_Pack_Upgrader::bulk_upgrade()}. Default empty array.
+        * @return array|bool|WP_Error The result of the upgrade, or a {@see wP_Error} object instead.
+        */
+       public function upgrade( $update = false, $args = array() ) {
+               if ( $update ) {
+                       $update = array( $update );
+               }
+
+               $results = $this->bulk_upgrade( $update, $args );
+
+               if ( ! is_array( $results ) ) {
+                       return $results;
+               }
+
+               return $results[0];
+       }
+
+       /**
+        * Bulk upgrade language packs.
+        *
+        * @since 3.7.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param array $language_updates Optional. Language pack updates. Default empty array.
+        * @param array $args {
+        *     Optional. Other arguments for upgrading multiple language packs. Default empty array
+        *
+        *     @type bool $clear_update_cache Whether to clear the update cache when done.
+        *                                    Default true.
+        * }
+        * @return array|bool|WP_Error Will return an array of results, or true if there are no updates,
+        *                                   false or WP_Error for initial errors.
+        */
+       public function bulk_upgrade( $language_updates = array(), $args = array() ) {
+               global $wp_filesystem;
+
+               $defaults = array(
+                       'clear_update_cache' => true,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
+
+               $this->init();
+               $this->upgrade_strings();
+
+               if ( ! $language_updates )
+                       $language_updates = wp_get_translation_updates();
+
+               if ( empty( $language_updates ) ) {
+                       $this->skin->header();
+                       $this->skin->before();
+                       $this->skin->set_result( true );
+                       $this->skin->feedback( 'up_to_date' );
+                       $this->skin->after();
+                       $this->skin->bulk_footer();
+                       $this->skin->footer();
+                       return true;
+               }
+
+               if ( 'upgrader_process_complete' == current_filter() )
+                       $this->skin->feedback( 'starting_upgrade' );
+
+               // Remove any existing upgrade filters from the plugin/theme upgraders #WP29425 & #WP29230
+               remove_all_filters( 'upgrader_pre_install' );
+               remove_all_filters( 'upgrader_clear_destination' );
+               remove_all_filters( 'upgrader_post_install' );
+               remove_all_filters( 'upgrader_source_selection' );
+
+               add_filter( 'upgrader_source_selection', array( $this, 'check_package' ), 10, 2 );
+
+               $this->skin->header();
+
+               // Connect to the Filesystem first.
+               $res = $this->fs_connect( array( WP_CONTENT_DIR, WP_LANG_DIR ) );
+               if ( ! $res ) {
+                       $this->skin->footer();
+                       return false;
+               }
+
+               $results = array();
+
+               $this->update_count = count( $language_updates );
+               $this->update_current = 0;
+
+               /*
+                * The filesystem's mkdir() is not recursive. Make sure WP_LANG_DIR exists,
+                * as we then may need to create a /plugins or /themes directory inside of it.
+                */
+               $remote_destination = $wp_filesystem->find_folder( WP_LANG_DIR );
+               if ( ! $wp_filesystem->exists( $remote_destination ) )
+                       if ( ! $wp_filesystem->mkdir( $remote_destination, FS_CHMOD_DIR ) )
+                               return new WP_Error( 'mkdir_failed_lang_dir', $this->strings['mkdir_failed'], $remote_destination );
+
+               foreach ( $language_updates as $language_update ) {
+
+                       $this->skin->language_update = $language_update;
+
+                       $destination = WP_LANG_DIR;
+                       if ( 'plugin' == $language_update->type )
+                               $destination .= '/plugins';
+                       elseif ( 'theme' == $language_update->type )
+                               $destination .= '/themes';
+
+                       $this->update_current++;
+
+                       $options = array(
+                               'package' => $language_update->package,
+                               'destination' => $destination,
+                               'clear_destination' => false,
+                               'abort_if_destination_exists' => false, // We expect the destination to exist.
+                               'clear_working' => true,
+                               'is_multi' => true,
+                               'hook_extra' => array(
+                                       'language_update_type' => $language_update->type,
+                                       'language_update' => $language_update,
+                               )
+                       );
+
+                       $result = $this->run( $options );
+
+                       $results[] = $this->result;
+
+                       // Prevent credentials auth screen from displaying multiple times.
+                       if ( false === $result )
+                               break;
+               }
+
+               $this->skin->bulk_footer();
+
+               $this->skin->footer();
+
+               // Clean up our hooks, in case something else does an upgrade on this connection.
+               remove_filter( 'upgrader_source_selection', array( $this, 'check_package' ) );
+
+               if ( $parsed_args['clear_update_cache'] ) {
+                       wp_clean_update_cache();
+               }
+
+               return $results;
+       }
+
+       /**
+        * Check the package source to make sure there are .mo and .po files.
+        *
+        * Hooked to the {@see 'upgrader_source_selection'} filter by
+        * {@see Language_Pack_Upgrader::bulk_upgrade()}.
+        *
+        * @since 3.7.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        *
+        * @param string|WP_Error $source
+        * @param string          $remote_source
+        */
+       public function check_package( $source, $remote_source ) {
+               global $wp_filesystem;
+
+               if ( is_wp_error( $source ) )
+                       return $source;
+
+               // Check that the folder contains a valid language.
+               $files = $wp_filesystem->dirlist( $remote_source );
+
+               // Check to see if a .po and .mo exist in the folder.
+               $po = $mo = false;
+               foreach ( (array) $files as $file => $filedata ) {
+                       if ( '.po' == substr( $file, -3 ) )
+                               $po = true;
+                       elseif ( '.mo' == substr( $file, -3 ) )
+                               $mo = true;
+               }
+
+               if ( ! $mo || ! $po )
+                       return new WP_Error( 'incompatible_archive_pomo', $this->strings['incompatible_archive'],
+                               __( 'The language pack is missing either the <code>.po</code> or <code>.mo</code> files.' ) );
+
+               return $source;
+       }
+
+       /**
+        * Get the name of an item being updated.
+        *
+        * @since 3.7.0
+        *
+        * @param object $update The data for an update.
+        * @return string The name of the item being updated.
+        */
+       public function get_name_for_update( $update ) {
+               switch ( $update->type ) {
+                       case 'core':
+                               return 'WordPress'; // Not translated
+
+                       case 'theme':
+                               $theme = wp_get_theme( $update->slug );
+                               if ( $theme->exists() )
+                                       return $theme->Get( 'Name' );
+                               break;
+                       case 'plugin':
+                               $plugin_data = get_plugins( '/' . $update->slug );
+                               $plugin_data = reset( $plugin_data );
+                               if ( $plugin_data )
+                                       return $plugin_data['Name'];
+                               break;
+               }
+               return '';
+       }
+
+}
+
+/**
+ * Core Upgrader class for WordPress. It allows for WordPress to upgrade itself in combination with the wp-admin/includes/update-core.php file
  *
  * @package WordPress
  * @subpackage Upgrader
  *
  * @package WordPress
  * @subpackage Upgrader
@@ -1005,39 +2053,87 @@ class Theme_Upgrader extends WP_Upgrader {
  */
 class Core_Upgrader extends WP_Upgrader {
 
  */
 class Core_Upgrader extends WP_Upgrader {
 
-       function upgrade_strings() {
+       /**
+        * Initialize the upgrade strings.
+        *
+        * @since 2.8.0
+        */
+       public function upgrade_strings() {
                $this->strings['up_to_date'] = __('WordPress is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the update&#8230;');
                $this->strings['copy_failed'] = __('Could not copy files.');
                $this->strings['copy_failed_space'] = __('Could not copy files. You may have run out of disk space.' );
                $this->strings['up_to_date'] = __('WordPress is at the latest version.');
                $this->strings['no_package'] = __('Update package not available.');
                $this->strings['downloading_package'] = __('Downloading update from <span class="code">%s</span>&#8230;');
                $this->strings['unpack_package'] = __('Unpacking the update&#8230;');
                $this->strings['copy_failed'] = __('Could not copy files.');
                $this->strings['copy_failed_space'] = __('Could not copy files. You may have run out of disk space.' );
-       }
+               $this->strings['start_rollback'] = __( 'Attempting to roll back to previous version.' );
+               $this->strings['rollback_was_required'] = __( 'Due to an error during updating, WordPress has rolled back to your previous version.' );
+       }
+
+       /**
+        * Upgrade WordPress core.
+        *
+        * @since 2.8.0
+        *
+        * @global WP_Filesystem_Base $wp_filesystem Subclass
+        * @global callback           $_wp_filesystem_direct_method
+        *
+        * @param object $current Response object for whether WordPress is current.
+        * @param array  $args {
+        *        Optional. Arguments for upgrading WordPress core. Default empty array.
+        *
+        *        @type bool $pre_check_md5    Whether to check the file checksums before
+        *                                     attempting the upgrade. Default true.
+        *        @type bool $attempt_rollback Whether to attempt to rollback the chances if
+        *                                     there is a problem. Default false.
+        *        @type bool $do_rollback      Whether to perform this "upgrade" as a rollback.
+        *                                     Default false.
+        * }
+        * @return null|false|WP_Error False or WP_Error on failure, null on success.
+        */
+       public function upgrade( $current, $args = array() ) {
+               global $wp_filesystem;
 
 
-       function upgrade($current) {
-               global $wp_filesystem, $wp_version;
+               include( ABSPATH . WPINC . '/version.php' ); // $wp_version;
+
+               $start_time = time();
+
+               $defaults = array(
+                       'pre_check_md5'    => true,
+                       'attempt_rollback' => false,
+                       'do_rollback'      => false,
+                       'allow_relaxed_file_ownership' => false,
+               );
+               $parsed_args = wp_parse_args( $args, $defaults );
 
                $this->init();
                $this->upgrade_strings();
 
 
                $this->init();
                $this->upgrade_strings();
 
-               if ( !empty($feedback) )
-                       add_filter('update_feedback', $feedback);
-
                // Is an update available?
                if ( !isset( $current->response ) || $current->response == 'latest' )
                        return new WP_Error('up_to_date', $this->strings['up_to_date']);
 
                // Is an update available?
                if ( !isset( $current->response ) || $current->response == 'latest' )
                        return new WP_Error('up_to_date', $this->strings['up_to_date']);
 
-               $res = $this->fs_connect( array(ABSPATH, WP_CONTENT_DIR) );
-               if ( is_wp_error($res) )
+               $res = $this->fs_connect( array( ABSPATH, WP_CONTENT_DIR ), $parsed_args['allow_relaxed_file_ownership'] );
+               if ( ! $res || is_wp_error( $res ) ) {
                        return $res;
                        return $res;
+               }
 
                $wp_dir = trailingslashit($wp_filesystem->abspath());
 
 
                $wp_dir = trailingslashit($wp_filesystem->abspath());
 
-               // If partial update is returned from the API, use that, unless we're doing a reinstall.
-               // If we cross the new_bundled version number, then use the new_bundled zip.
-               // Don't though if the constant is set to skip bundled items.
-               // If the API returns a no_content zip, go with it. Finally, default to the full zip.
-               if ( $current->packages->partial && 'reinstall' != $current->response && $wp_version == $current->partial_version )
+               $partial = true;
+               if ( $parsed_args['do_rollback'] )
+                       $partial = false;
+               elseif ( $parsed_args['pre_check_md5'] && ! $this->check_files() )
+                       $partial = false;
+
+               /*
+                * If partial update is returned from the API, use that, unless we're doing
+                * a reinstall. If we cross the new_bundled version number, then use
+                * the new_bundled zip. Don't though if the constant is set to skip bundled items.
+                * If the API returns a no_content zip, go with it. Finally, default to the full zip.
+                */
+               if ( $parsed_args['do_rollback'] && $current->packages->rollback )
+                       $to_download = 'rollback';
+               elseif ( $current->packages->partial && 'reinstall' != $current->response && $wp_version == $current->partial_version && $partial )
                        $to_download = 'partial';
                elseif ( $current->packages->new_bundled && version_compare( $wp_version, $current->new_bundled, '<' )
                        && ( ! defined( 'CORE_UPGRADE_SKIP_NEW_BUNDLED' ) || ! CORE_UPGRADE_SKIP_NEW_BUNDLED ) )
                        $to_download = 'partial';
                elseif ( $current->packages->new_bundled && version_compare( $wp_version, $current->new_bundled, '<' )
                        && ( ! defined( 'CORE_UPGRADE_SKIP_NEW_BUNDLED' ) || ! CORE_UPGRADE_SKIP_NEW_BUNDLED ) )
@@ -1058,616 +2154,1249 @@ class Core_Upgrader extends WP_Upgrader {
                // Copy update-core.php from the new version into place.
                if ( !$wp_filesystem->copy($working_dir . '/wordpress/wp-admin/includes/update-core.php', $wp_dir . 'wp-admin/includes/update-core.php', true) ) {
                        $wp_filesystem->delete($working_dir, true);
                // Copy update-core.php from the new version into place.
                if ( !$wp_filesystem->copy($working_dir . '/wordpress/wp-admin/includes/update-core.php', $wp_dir . 'wp-admin/includes/update-core.php', true) ) {
                        $wp_filesystem->delete($working_dir, true);
-                       return new WP_Error('copy_failed', $this->strings['copy_failed']);
+                       return new WP_Error( 'copy_failed_for_update_core_file', __( 'The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.' ), 'wp-admin/includes/update-core.php' );
                }
                $wp_filesystem->chmod($wp_dir . 'wp-admin/includes/update-core.php', FS_CHMOD_FILE);
 
                }
                $wp_filesystem->chmod($wp_dir . 'wp-admin/includes/update-core.php', FS_CHMOD_FILE);
 
-               require(ABSPATH . 'wp-admin/includes/update-core.php');
+               require_once( ABSPATH . 'wp-admin/includes/update-core.php' );
 
                if ( ! function_exists( 'update_core' ) )
                        return new WP_Error( 'copy_failed_space', $this->strings['copy_failed_space'] );
 
 
                if ( ! function_exists( 'update_core' ) )
                        return new WP_Error( 'copy_failed_space', $this->strings['copy_failed_space'] );
 
-               return update_core($working_dir, $wp_dir);
-       }
-
-}
+               $result = update_core( $working_dir, $wp_dir );
+
+               // In the event of an issue, we may be able to roll back.
+               if ( $parsed_args['attempt_rollback'] && $current->packages->rollback && ! $parsed_args['do_rollback'] ) {
+                       $try_rollback = false;
+                       if ( is_wp_error( $result ) ) {
+                               $error_code = $result->get_error_code();
+                               /*
+                                * Not all errors are equal. These codes are critical: copy_failed__copy_dir,
+                                * mkdir_failed__copy_dir, copy_failed__copy_dir_retry, and disk_full.
+                                * do_rollback allows for update_core() to trigger a rollback if needed.
+                                */
+                               if ( false !== strpos( $error_code, 'do_rollback' ) )
+                                       $try_rollback = true;
+                               elseif ( false !== strpos( $error_code, '__copy_dir' ) )
+                                       $try_rollback = true;
+                               elseif ( 'disk_full' === $error_code )
+                                       $try_rollback = true;
+                       }
 
 
-/**
- * Generic Skin for the WordPress Upgrader classes. This skin is designed to be extended for specific purposes.
- *
- * @TODO More Detailed docs, for methods as well.
- *
- * @package WordPress
- * @subpackage Upgrader
- * @since 2.8.0
- */
-class WP_Upgrader_Skin {
+                       if ( $try_rollback ) {
+                               /** This filter is documented in wp-admin/includes/update-core.php */
+                               apply_filters( 'update_feedback', $result );
 
 
-       var $upgrader;
-       var $done_header = false;
-       var $result = false;
+                               /** This filter is documented in wp-admin/includes/update-core.php */
+                               apply_filters( 'update_feedback', $this->strings['start_rollback'] );
 
 
-       function __construct($args = array()) {
-               $defaults = array( 'url' => '', 'nonce' => '', 'title' => '', 'context' => false );
-               $this->options = wp_parse_args($args, $defaults);
-       }
+                               $rollback_result = $this->upgrade( $current, array_merge( $parsed_args, array( 'do_rollback' => true ) ) );
 
 
-       function set_upgrader(&$upgrader) {
-               if ( is_object($upgrader) )
-                       $this->upgrader =& $upgrader;
-               $this->add_strings();
-       }
+                               $original_result = $result;
+                               $result = new WP_Error( 'rollback_was_required', $this->strings['rollback_was_required'], (object) array( 'update' => $original_result, 'rollback' => $rollback_result ) );
+                       }
+               }
 
 
-       function add_strings() {
-       }
+               /** This action is documented in wp-admin/includes/class-wp-upgrader.php */
+               do_action( 'upgrader_process_complete', $this, array( 'action' => 'update', 'type' => 'core' ) );
+
+               // Clear the current updates
+               delete_site_transient( 'update_core' );
+
+               if ( ! $parsed_args['do_rollback'] ) {
+                       $stats = array(
+                               'update_type'      => $current->response,
+                               'success'          => true,
+                               'fs_method'        => $wp_filesystem->method,
+                               'fs_method_forced' => defined( 'FS_METHOD' ) || has_filter( 'filesystem_method' ),
+                               'fs_method_direct' => !empty( $GLOBALS['_wp_filesystem_direct_method'] ) ? $GLOBALS['_wp_filesystem_direct_method'] : '',
+                               'time_taken'       => time() - $start_time,
+                               'reported'         => $wp_version,
+                               'attempted'        => $current->version,
+                       );
 
 
-       function set_result($result) {
-               $this->result = $result;
-       }
+                       if ( is_wp_error( $result ) ) {
+                               $stats['success'] = false;
+                               // Did a rollback occur?
+                               if ( ! empty( $try_rollback ) ) {
+                                       $stats['error_code'] = $original_result->get_error_code();
+                                       $stats['error_data'] = $original_result->get_error_data();
+                                       // Was the rollback successful? If not, collect its error too.
+                                       $stats['rollback'] = ! is_wp_error( $rollback_result );
+                                       if ( is_wp_error( $rollback_result ) ) {
+                                               $stats['rollback_code'] = $rollback_result->get_error_code();
+                                               $stats['rollback_data'] = $rollback_result->get_error_data();
+                                       }
+                               } else {
+                                       $stats['error_code'] = $result->get_error_code();
+                                       $stats['error_data'] = $result->get_error_data();
+                               }
+                       }
 
 
-       function request_filesystem_credentials($error = false) {
-               $url = $this->options['url'];
-               $context = $this->options['context'];
-               if ( !empty($this->options['nonce']) )
-                       $url = wp_nonce_url($url, $this->options['nonce']);
-               return request_filesystem_credentials($url, '', $error, $context); //Possible to bring inline, Leaving as is for now.
-       }
+                       wp_version_check( $stats );
+               }
 
 
-       function header() {
-               if ( $this->done_header )
-                       return;
-               $this->done_header = true;
-               echo '<div class="wrap">';
-               echo screen_icon();
-               echo '<h2>' . $this->options['title'] . '</h2>';
-       }
-       function footer() {
-               echo '</div>';
+               return $result;
        }
 
        }
 
-       function error($errors) {
-               if ( ! $this->done_header )
-                       $this->header();
-               if ( is_string($errors) ) {
-                       $this->feedback($errors);
-               } elseif ( is_wp_error($errors) && $errors->get_error_code() ) {
-                       foreach ( $errors->get_error_messages() as $message ) {
-                               if ( $errors->get_error_data() )
-                                       $this->feedback($message . ' ' . $errors->get_error_data() );
-                               else
-                                       $this->feedback($message);
+       /**
+        * Determines if this WordPress Core version should update to an offered version or not.
+        *
+        * @since 3.7.0
+        *
+        * @static
+        *
+        * @param string $offered_ver The offered version, of the format x.y.z.
+        * @return bool True if we should update to the offered version, otherwise false.
+        */
+       public static function should_update_to_version( $offered_ver ) {
+               include( ABSPATH . WPINC . '/version.php' ); // $wp_version; // x.y.z
+
+               $current_branch = implode( '.', array_slice( preg_split( '/[.-]/', $wp_version  ), 0, 2 ) ); // x.y
+               $new_branch     = implode( '.', array_slice( preg_split( '/[.-]/', $offered_ver ), 0, 2 ) ); // x.y
+               $current_is_development_version = (bool) strpos( $wp_version, '-' );
+
+               // Defaults:
+               $upgrade_dev   = true;
+               $upgrade_minor = true;
+               $upgrade_major = false;
+
+               // WP_AUTO_UPDATE_CORE = true (all), 'minor', false.
+               if ( defined( 'WP_AUTO_UPDATE_CORE' ) ) {
+                       if ( false === WP_AUTO_UPDATE_CORE ) {
+                               // Defaults to turned off, unless a filter allows it
+                               $upgrade_dev = $upgrade_minor = $upgrade_major = false;
+                       } elseif ( true === WP_AUTO_UPDATE_CORE ) {
+                               // ALL updates for core
+                               $upgrade_dev = $upgrade_minor = $upgrade_major = true;
+                       } elseif ( 'minor' === WP_AUTO_UPDATE_CORE ) {
+                               // Only minor updates for core
+                               $upgrade_dev = $upgrade_major = false;
+                               $upgrade_minor = true;
                        }
                }
                        }
                }
-       }
 
 
-       function feedback($string) {
-               if ( isset( $this->upgrader->strings[$string] ) )
-                       $string = $this->upgrader->strings[$string];
+               // 1: If we're already on that version, not much point in updating?
+               if ( $offered_ver == $wp_version )
+                       return false;
 
 
-               if ( strpos($string, '%') !== false ) {
-                       $args = func_get_args();
-                       $args = array_splice($args, 1);
-                       if ( !empty($args) )
-                               $string = vsprintf($string, $args);
-               }
-               if ( empty($string) )
-                       return;
-               show_message($string);
-       }
-       function before() {}
-       function after() {}
+               // 2: If we're running a newer version, that's a nope
+               if ( version_compare( $wp_version, $offered_ver, '>' ) )
+                       return false;
 
 
-}
+               $failure_data = get_site_option( 'auto_core_update_failed' );
+               if ( $failure_data ) {
+                       // If this was a critical update failure, cannot update.
+                       if ( ! empty( $failure_data['critical'] ) )
+                               return false;
 
 
-/**
- * Plugin Upgrader Skin for WordPress Plugin Upgrades.
- *
- * @TODO More Detailed docs, for methods as well.
- *
- * @package WordPress
- * @subpackage Upgrader
- * @since 2.8.0
- */
-class Plugin_Upgrader_Skin extends WP_Upgrader_Skin {
-       var $plugin = '';
-       var $plugin_active = false;
-       var $plugin_network_active = false;
+                       // Don't claim we can update on update-core.php if we have a non-critical failure logged.
+                       if ( $wp_version == $failure_data['current'] && false !== strpos( $offered_ver, '.1.next.minor' ) )
+                               return false;
 
 
-       function __construct($args = array()) {
-               $defaults = array( 'url' => '', 'plugin' => '', 'nonce' => '', 'title' => __('Update Plugin') );
-               $args = wp_parse_args($args, $defaults);
+                       // Cannot update if we're retrying the same A to B update that caused a non-critical failure.
+                       // Some non-critical failures do allow retries, like download_failed.
+                       // 3.7.1 => 3.7.2 resulted in files_not_writable, if we are still on 3.7.1 and still trying to update to 3.7.2.
+                       if ( empty( $failure_data['retry'] ) && $wp_version == $failure_data['current'] && $offered_ver == $failure_data['attempted'] )
+                               return false;
+               }
 
 
-               $this->plugin = $args['plugin'];
+               // 3: 3.7-alpha-25000 -> 3.7-alpha-25678 -> 3.7-beta1 -> 3.7-beta2
+               if ( $current_is_development_version ) {
+
+                       /**
+                        * Filter whether to enable automatic core updates for development versions.
+                        *
+                        * @since 3.7.0
+                        *
+                        * @param bool $upgrade_dev Whether to enable automatic updates for
+                        *                          development versions.
+                        */
+                       if ( ! apply_filters( 'allow_dev_auto_core_updates', $upgrade_dev ) )
+                               return false;
+                       // Else fall through to minor + major branches below.
+               }
 
 
-               $this->plugin_active = is_plugin_active( $this->plugin );
-               $this->plugin_network_active = is_plugin_active_for_network( $this->plugin );
+               // 4: Minor In-branch updates (3.7.0 -> 3.7.1 -> 3.7.2 -> 3.7.4)
+               if ( $current_branch == $new_branch ) {
+
+                       /**
+                        * Filter whether to enable minor automatic core updates.
+                        *
+                        * @since 3.7.0
+                        *
+                        * @param bool $upgrade_minor Whether to enable minor automatic core updates.
+                        */
+                       return apply_filters( 'allow_minor_auto_core_updates', $upgrade_minor );
+               }
+
+               // 5: Major version updates (3.7.0 -> 3.8.0 -> 3.9.1)
+               if ( version_compare( $new_branch, $current_branch, '>' ) ) {
+
+                       /**
+                        * Filter whether to enable major automatic core updates.
+                        *
+                        * @since 3.7.0
+                        *
+                        * @param bool $upgrade_major Whether to enable major automatic core updates.
+                        */
+                       return apply_filters( 'allow_major_auto_core_updates', $upgrade_major );
+               }
 
 
-               parent::__construct($args);
+               // If we're not sure, we don't want it
+               return false;
        }
 
        }
 
-       function after() {
-               $this->plugin = $this->upgrader->plugin_info();
-               if ( !empty($this->plugin) && !is_wp_error($this->result) && $this->plugin_active ){
-                       echo '<iframe style="border:0;overflow:hidden" width="100%" height="170px" src="' . wp_nonce_url('update.php?action=activate-plugin&networkwide=' . $this->plugin_network_active . '&plugin=' . $this->plugin, 'activate-plugin_' . $this->plugin) .'"></iframe>';
-               }
+       /**
+        * Compare the disk file checksums agains the expected checksums.
+        *
+        * @since 3.7.0
+        *
+        * @global string $wp_version
+        * @global string $wp_local_package
+        *
+        * @return bool True if the checksums match, otherwise false.
+        */
+       public function check_files() {
+               global $wp_version, $wp_local_package;
 
 
-               $update_actions =  array(
-                       'activate_plugin' => '<a href="' . wp_nonce_url('plugins.php?action=activate&amp;plugin=' . $this->plugin, 'activate-plugin_' . $this->plugin) . '" title="' . esc_attr__('Activate this plugin') . '" target="_parent">' . __('Activate Plugin') . '</a>',
-                       'plugins_page' => '<a href="' . self_admin_url('plugins.php') . '" title="' . esc_attr__('Go to plugins page') . '" target="_parent">' . __('Return to Plugins page') . '</a>'
-               );
-               if ( $this->plugin_active || ! $this->result || is_wp_error( $this->result ) || ! current_user_can( 'activate_plugins' ) )
-                       unset( $update_actions['activate_plugin'] );
+               $checksums = get_core_checksums( $wp_version, isset( $wp_local_package ) ? $wp_local_package : 'en_US' );
 
 
-               $update_actions = apply_filters('update_plugin_complete_actions', $update_actions, $this->plugin);
-               if ( ! empty($update_actions) )
-                       $this->feedback(implode(' | ', (array)$update_actions));
-       }
+               if ( ! is_array( $checksums ) )
+                       return false;
 
 
-       function before() {
-               if ( $this->upgrader->show_before ) {
-                       echo $this->upgrader->show_before;
-                       $this->upgrader->show_before = '';
+               foreach ( $checksums as $file => $checksum ) {
+                       // Skip files which get updated
+                       if ( 'wp-content' == substr( $file, 0, 10 ) )
+                               continue;
+                       if ( ! file_exists( ABSPATH . $file ) || md5_file( ABSPATH . $file ) !== $checksum )
+                               return false;
                }
                }
+
+               return true;
        }
 }
 
 /**
        }
 }
 
 /**
- * Plugin Upgrader Skin for WordPress Plugin Upgrades.
+ * Upgrade Skin helper for File uploads. This class handles the upload process and passes it as if it's a local file to the Upgrade/Installer functions.
  *
  * @package WordPress
  * @subpackage Upgrader
  *
  * @package WordPress
  * @subpackage Upgrader
- * @since 3.0.0
+ * @since 2.8.0
  */
  */
-class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
-       var $in_loop = false;
-       var $error = false;
+class File_Upload_Upgrader {
 
 
-       function __construct($args = array()) {
-               $defaults = array( 'url' => '', 'nonce' => '' );
-               $args = wp_parse_args($args, $defaults);
+       /**
+        * The full path to the file package.
+        *
+        * @since 2.8.0
+        * @var string $package
+        */
+       public $package;
+
+       /**
+        * The name of the file.
+        *
+        * @since 2.8.0
+        * @var string $filename
+        */
+       public $filename;
+
+       /**
+        * The ID of the attachment post for this file.
+        *
+        * @since 3.3.0
+        * @var int $id
+        */
+       public $id = 0;
+
+       /**
+        * Construct the upgrader for a form.
+        *
+        * @since 2.8.0
+        *
+        * @param string $form      The name of the form the file was uploaded from.
+        * @param string $urlholder The name of the `GET` parameter that holds the filename.
+        */
+       public function __construct( $form, $urlholder ) {
 
 
-               parent::__construct($args);
-       }
+               if ( empty($_FILES[$form]['name']) && empty($_GET[$urlholder]) )
+                       wp_die(__('Please select a file'));
 
 
-       function add_strings() {
-               $this->upgrader->strings['skin_upgrade_start'] = __('The update process is starting. This process may take a while on some hosts, so please be patient.');
-               $this->upgrader->strings['skin_update_failed_error'] = __('An error occurred while updating %1$s: <strong>%2$s</strong>.');
-               $this->upgrader->strings['skin_update_failed'] = __('The update of %1$s failed.');
-               $this->upgrader->strings['skin_update_successful'] = __('%1$s updated successfully.').' <a onclick="%2$s" href="#" class="hide-if-no-js"><span>'.__('Show Details').'</span><span class="hidden">'.__('Hide Details').'</span>.</a>';
-               $this->upgrader->strings['skin_upgrade_end'] = __('All updates have been completed.');
-       }
+               //Handle a newly uploaded file, Else assume it's already been uploaded
+               if ( ! empty($_FILES) ) {
+                       $overrides = array( 'test_form' => false, 'test_type' => false );
+                       $file = wp_handle_upload( $_FILES[$form], $overrides );
+
+                       if ( isset( $file['error'] ) )
+                               wp_die( $file['error'] );
+
+                       $this->filename = $_FILES[$form]['name'];
+                       $this->package = $file['file'];
+
+                       // Construct the object array
+                       $object = array(
+                               'post_title' => $this->filename,
+                               'post_content' => $file['url'],
+                               'post_mime_type' => $file['type'],
+                               'guid' => $file['url'],
+                               'context' => 'upgrader',
+                               'post_status' => 'private'
+                       );
+
+                       // Save the data.
+                       $this->id = wp_insert_attachment( $object, $file['file'] );
+
+                       // Schedule a cleanup for 2 hours from now in case of failed install.
+                       wp_schedule_single_event( time() + 2 * HOUR_IN_SECONDS, 'upgrader_scheduled_cleanup', array( $this->id ) );
+
+               } elseif ( is_numeric( $_GET[$urlholder] ) ) {
+                       // Numeric Package = previously uploaded file, see above.
+                       $this->id = (int) $_GET[$urlholder];
+                       $attachment = get_post( $this->id );
+                       if ( empty($attachment) )
+                               wp_die(__('Please select a file'));
 
 
-       function feedback($string) {
-               if ( isset( $this->upgrader->strings[$string] ) )
-                       $string = $this->upgrader->strings[$string];
+                       $this->filename = $attachment->post_title;
+                       $this->package = get_attached_file( $attachment->ID );
+               } else {
+                       // Else, It's set to something, Back compat for plugins using the old (pre-3.3) File_Uploader handler.
+                       if ( ! ( ( $uploads = wp_upload_dir() ) && false === $uploads['error'] ) )
+                               wp_die( $uploads['error'] );
 
 
-               if ( strpos($string, '%') !== false ) {
-                       $args = func_get_args();
-                       $args = array_splice($args, 1);
-                       if ( !empty($args) )
-                               $string = vsprintf($string, $args);
+                       $this->filename = $_GET[$urlholder];
+                       $this->package = $uploads['basedir'] . '/' . $this->filename;
                }
                }
-               if ( empty($string) )
-                       return;
-               if ( $this->in_loop )
-                       echo "$string<br />\n";
-               else
-                       echo "<p>$string</p>\n";
        }
 
        }
 
-       function header() {
-               // Nothing, This will be displayed within a iframe.
-       }
+       /**
+        * Delete the attachment/uploaded file.
+        *
+        * @since 3.2.2
+        *
+        * @return bool Whether the cleanup was successful.
+        */
+       public function cleanup() {
+               if ( $this->id )
+                       wp_delete_attachment( $this->id );
+
+               elseif ( file_exists( $this->package ) )
+                       return @unlink( $this->package );
 
 
-       function footer() {
-               // Nothing, This will be displayed within a iframe.
+               return true;
        }
        }
-       function error($error) {
-               if ( is_string($error) && isset( $this->upgrader->strings[$error] ) )
-                       $this->error = $this->upgrader->strings[$error];
-
-               if ( is_wp_error($error) ) {
-                       foreach ( $error->get_error_messages() as $emessage ) {
-                               if ( $error->get_error_data() )
-                                       $messages[] = $emessage . ' ' . $error->get_error_data();
-                               else
-                                       $messages[] = $emessage;
-                       }
-                       $this->error = implode(', ', $messages);
+}
+
+/**
+ * The WordPress automatic background updater.
+ *
+ * @package WordPress
+ * @subpackage Upgrader
+ * @since 3.7.0
+ */
+class WP_Automatic_Updater {
+
+       /**
+        * Tracks update results during processing.
+        *
+        * @var array
+        */
+       protected $update_results = array();
+
+       /**
+        * Whether the entire automatic updater is disabled.
+        *
+        * @since 3.7.0
+        */
+       public function is_disabled() {
+               // Background updates are disabled if you don't want file changes.
+               if ( defined( 'DISALLOW_FILE_MODS' ) && DISALLOW_FILE_MODS )
+                       return true;
+
+               if ( defined( 'WP_INSTALLING' ) )
+                       return true;
+
+               // More fine grained control can be done through the WP_AUTO_UPDATE_CORE constant and filters.
+               $disabled = defined( 'AUTOMATIC_UPDATER_DISABLED' ) && AUTOMATIC_UPDATER_DISABLED;
+
+               /**
+                * Filter whether to entirely disable background updates.
+                *
+                * There are more fine-grained filters and controls for selective disabling.
+                * This filter parallels the AUTOMATIC_UPDATER_DISABLED constant in name.
+                *
+                * This also disables update notification emails. That may change in the future.
+                *
+                * @since 3.7.0
+                *
+                * @param bool $disabled Whether the updater should be disabled.
+                */
+               return apply_filters( 'automatic_updater_disabled', $disabled );
+       }
+
+       /**
+        * Check for version control checkouts.
+        *
+        * Checks for Subversion, Git, Mercurial, and Bazaar. It recursively looks up the
+        * filesystem to the top of the drive, erring on the side of detecting a VCS
+        * checkout somewhere.
+        *
+        * ABSPATH is always checked in addition to whatever $context is (which may be the
+        * wp-content directory, for example). The underlying assumption is that if you are
+        * using version control *anywhere*, then you should be making decisions for
+        * how things get updated.
+        *
+        * @since 3.7.0
+        *
+        * @param string $context The filesystem path to check, in addition to ABSPATH.
+        */
+       public function is_vcs_checkout( $context ) {
+               $context_dirs = array( untrailingslashit( $context ) );
+               if ( $context !== ABSPATH )
+                       $context_dirs[] = untrailingslashit( ABSPATH );
+
+               $vcs_dirs = array( '.svn', '.git', '.hg', '.bzr' );
+               $check_dirs = array();
+
+               foreach ( $context_dirs as $context_dir ) {
+                       // Walk up from $context_dir to the root.
+                       do {
+                               $check_dirs[] = $context_dir;
+
+                               // Once we've hit '/' or 'C:\', we need to stop. dirname will keep returning the input here.
+                               if ( $context_dir == dirname( $context_dir ) )
+                                       break;
+
+                       // Continue one level at a time.
+                       } while ( $context_dir = dirname( $context_dir ) );
                }
                }
-               echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js($this->upgrader->update_current) . '\').hide();</script>';
-       }
 
 
-       function bulk_header() {
-               $this->feedback('skin_upgrade_start');
-       }
+               $check_dirs = array_unique( $check_dirs );
 
 
-       function bulk_footer() {
-               $this->feedback('skin_upgrade_end');
-       }
+               // Search all directories we've found for evidence of version control.
+               foreach ( $vcs_dirs as $vcs_dir ) {
+                       foreach ( $check_dirs as $check_dir ) {
+                               if ( $checkout = @is_dir( rtrim( $check_dir, '\\/' ) . "/$vcs_dir" ) )
+                                       break 2;
+                       }
+               }
 
 
-       function before($title = '') {
-               $this->in_loop = true;
-               printf( '<h4>' . $this->upgrader->strings['skin_before_update_header'] . ' <span class="spinner waiting-' . $this->upgrader->update_current . '"></span></h4>',  $title, $this->upgrader->update_current, $this->upgrader->update_count);
-               echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js($this->upgrader->update_current) . '\').css("display", "inline-block");</script>';
-               echo '<div class="update-messages hide-if-js" id="progress-' . esc_attr($this->upgrader->update_current) . '"><p>';
-               $this->flush_output();
-       }
+               /**
+                * Filter whether the automatic updater should consider a filesystem
+                * location to be potentially managed by a version control system.
+                *
+                * @since 3.7.0
+                *
+                * @param bool $checkout  Whether a VCS checkout was discovered at $context
+                *                        or ABSPATH, or anywhere higher.
+                * @param string $context The filesystem context (a path) against which
+                *                        filesystem status should be checked.
+                */
+               return apply_filters( 'automatic_updates_is_vcs_checkout', $checkout, $context );
+       }
+
+       /**
+        * Tests to see if we can and should update a specific item.
+        *
+        * @since 3.7.0
+        *
+        * @global wpdb $wpdb
+        *
+        * @param string $type    The type of update being checked: 'core', 'theme',
+        *                        'plugin', 'translation'.
+        * @param object $item    The update offer.
+        * @param string $context The filesystem context (a path) against which filesystem
+        *                        access and status should be checked.
+        */
+       public function should_update( $type, $item, $context ) {
+               // Used to see if WP_Filesystem is set up to allow unattended updates.
+               $skin = new Automatic_Upgrader_Skin;
+
+               if ( $this->is_disabled() )
+                       return false;
 
 
-       function after($title = '') {
-               echo '</p></div>';
-               if ( $this->error || ! $this->result ) {
-                       if ( $this->error )
-                               echo '<div class="error"><p>' . sprintf($this->upgrader->strings['skin_update_failed_error'], $title, $this->error) . '</p></div>';
-                       else
-                               echo '<div class="error"><p>' . sprintf($this->upgrader->strings['skin_update_failed'], $title) . '</p></div>';
+               // Only relax the filesystem checks when the update doesn't include new files
+               $allow_relaxed_file_ownership = false;
+               if ( 'core' == $type && isset( $item->new_files ) && ! $item->new_files ) {
+                       $allow_relaxed_file_ownership = true;
+               }
 
 
-                       echo '<script type="text/javascript">jQuery(\'#progress-' . esc_js($this->upgrader->update_current) . '\').show();</script>';
+               // If we can't do an auto core update, we may still be able to email the user.
+               if ( ! $skin->request_filesystem_credentials( false, $context, $allow_relaxed_file_ownership ) || $this->is_vcs_checkout( $context ) ) {
+                       if ( 'core' == $type )
+                               $this->send_core_update_notification_email( $item );
+                       return false;
                }
                }
-               if ( !empty($this->result) && !is_wp_error($this->result) ) {
-                       echo '<div class="updated"><p>' . sprintf($this->upgrader->strings['skin_update_successful'], $title, 'jQuery(\'#progress-' . esc_js($this->upgrader->update_current) . '\').toggle();jQuery(\'span\', this).toggle(); return false;') . '</p></div>';
-                       echo '<script type="text/javascript">jQuery(\'.waiting-' . esc_js($this->upgrader->update_current) . '\').hide();</script>';
+
+               // Next up, is this an item we can update?
+               if ( 'core' == $type )
+                       $update = Core_Upgrader::should_update_to_version( $item->current );
+               else
+                       $update = ! empty( $item->autoupdate );
+
+               /**
+                * Filter whether to automatically update core, a plugin, a theme, or a language.
+                *
+                * The dynamic portion of the hook name, `$type`, refers to the type of update
+                * being checked. Can be 'core', 'theme', 'plugin', or 'translation'.
+                *
+                * Generally speaking, plugins, themes, and major core versions are not updated
+                * by default, while translations and minor and development versions for core
+                * are updated by default.
+                *
+                * See the {@see 'allow_dev_auto_core_updates', {@see 'allow_minor_auto_core_updates'},
+                * and {@see 'allow_major_auto_core_updates'} filters for a more straightforward way to
+                * adjust core updates.
+                *
+                * @since 3.7.0
+                *
+                * @param bool   $update Whether to update.
+                * @param object $item   The update offer.
+                */
+               $update = apply_filters( 'auto_update_' . $type, $update, $item );
+
+               if ( ! $update ) {
+                       if ( 'core' == $type )
+                               $this->send_core_update_notification_email( $item );
+                       return false;
                }
 
                }
 
-               $this->reset();
-               $this->flush_output();
-       }
+               // If it's a core update, are we actually compatible with its requirements?
+               if ( 'core' == $type ) {
+                       global $wpdb;
 
 
-       function reset() {
-               $this->in_loop = false;
-               $this->error = false;
-       }
+                       $php_compat = version_compare( phpversion(), $item->php_version, '>=' );
+                       if ( file_exists( WP_CONTENT_DIR . '/db.php' ) && empty( $wpdb->is_mysql ) )
+                               $mysql_compat = true;
+                       else
+                               $mysql_compat = version_compare( $wpdb->db_version(), $item->mysql_version, '>=' );
 
 
-       function flush_output() {
-               wp_ob_end_flush_all();
-               flush();
+                       if ( ! $php_compat || ! $mysql_compat )
+                               return false;
+               }
+
+               return true;
        }
        }
-}
 
 
-class Bulk_Plugin_Upgrader_Skin extends Bulk_Upgrader_Skin {
-       var $plugin_info = array(); // Plugin_Upgrader::bulk() will fill this in.
+       /**
+        * Notifies an administrator of a core update.
+        *
+        * @since 3.7.0
+        *
+        * @param object $item The update offer.
+        */
+       protected function send_core_update_notification_email( $item ) {
+               $notified = get_site_option( 'auto_core_update_notified' );
 
 
-       function __construct($args = array()) {
-               parent::__construct($args);
-       }
+               // Don't notify if we've already notified the same email address of the same version.
+               if ( $notified && $notified['email'] == get_site_option( 'admin_email' ) && $notified['version'] == $item->current )
+                       return false;
 
 
-       function add_strings() {
-               parent::add_strings();
-               $this->upgrader->strings['skin_before_update_header'] = __('Updating Plugin %1$s (%2$d/%3$d)');
-       }
+               // See if we need to notify users of a core update.
+               $notify = ! empty( $item->notify_email );
+
+               /**
+                * Filter whether to notify the site administrator of a new core update.
+                *
+                * By default, administrators are notified when the update offer received
+                * from WordPress.org sets a particular flag. This allows some discretion
+                * in if and when to notify.
+                *
+                * This filter is only evaluated once per release. If the same email address
+                * was already notified of the same new version, WordPress won't repeatedly
+                * email the administrator.
+                *
+                * This filter is also used on about.php to check if a plugin has disabled
+                * these notifications.
+                *
+                * @since 3.7.0
+                *
+                * @param bool   $notify Whether the site administrator is notified.
+                * @param object $item   The update offer.
+                */
+               if ( ! apply_filters( 'send_core_update_notification_email', $notify, $item ) )
+                       return false;
 
 
-       function before() {
-               parent::before($this->plugin_info['Title']);
+               $this->send_email( 'manual', $item );
+               return true;
        }
 
        }
 
-       function after() {
-               parent::after($this->plugin_info['Title']);
-       }
-       function bulk_footer() {
-               parent::bulk_footer();
-               $update_actions =  array(
-                       'plugins_page' => '<a href="' . self_admin_url('plugins.php') . '" title="' . esc_attr__('Go to plugins page') . '" target="_parent">' . __('Return to Plugins page') . '</a>',
-                       'updates_page' => '<a href="' . self_admin_url('update-core.php') . '" title="' . esc_attr__('Go to WordPress Updates page') . '" target="_parent">' . __('Return to WordPress Updates') . '</a>'
-               );
-               if ( ! current_user_can( 'activate_plugins' ) )
-                       unset( $update_actions['plugins_page'] );
+       /**
+        * Update an item, if appropriate.
+        *
+        * @since 3.7.0
+        *
+        * @param string $type The type of update being checked: 'core', 'theme', 'plugin', 'translation'.
+        * @param object $item The update offer.
+        *
+        * @return null|WP_Error
+        */
+       public function update( $type, $item ) {
+               $skin = new Automatic_Upgrader_Skin;
+
+               switch ( $type ) {
+                       case 'core':
+                               // The Core upgrader doesn't use the Upgrader's skin during the actual main part of the upgrade, instead, firing a filter.
+                               add_filter( 'update_feedback', array( $skin, 'feedback' ) );
+                               $upgrader = new Core_Upgrader( $skin );
+                               $context  = ABSPATH;
+                               break;
+                       case 'plugin':
+                               $upgrader = new Plugin_Upgrader( $skin );
+                               $context  = WP_PLUGIN_DIR; // We don't support custom Plugin directories, or updates for WPMU_PLUGIN_DIR
+                               break;
+                       case 'theme':
+                               $upgrader = new Theme_Upgrader( $skin );
+                               $context  = get_theme_root( $item->theme );
+                               break;
+                       case 'translation':
+                               $upgrader = new Language_Pack_Upgrader( $skin );
+                               $context  = WP_CONTENT_DIR; // WP_LANG_DIR;
+                               break;
+               }
 
 
-               $update_actions = apply_filters('update_bulk_plugins_complete_actions', $update_actions, $this->plugin_info);
-               if ( ! empty($update_actions) )
-                       $this->feedback(implode(' | ', (array)$update_actions));
-       }
-}
+               // Determine whether we can and should perform this update.
+               if ( ! $this->should_update( $type, $item, $context ) )
+                       return false;
 
 
-class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
-       var $theme_info = array(); // Theme_Upgrader::bulk() will fill this in.
+               $upgrader_item = $item;
+               switch ( $type ) {
+                       case 'core':
+                               $skin->feedback( __( 'Updating to WordPress %s' ), $item->version );
+                               $item_name = sprintf( __( 'WordPress %s' ), $item->version );
+                               break;
+                       case 'theme':
+                               $upgrader_item = $item->theme;
+                               $theme = wp_get_theme( $upgrader_item );
+                               $item_name = $theme->Get( 'Name' );
+                               $skin->feedback( __( 'Updating theme: %s' ), $item_name );
+                               break;
+                       case 'plugin':
+                               $upgrader_item = $item->plugin;
+                               $plugin_data = get_plugin_data( $context . '/' . $upgrader_item );
+                               $item_name = $plugin_data['Name'];
+                               $skin->feedback( __( 'Updating plugin: %s' ), $item_name );
+                               break;
+                       case 'translation':
+                               $language_item_name = $upgrader->get_name_for_update( $item );
+                               $item_name = sprintf( __( 'Translations for %s' ), $language_item_name );
+                               $skin->feedback( sprintf( __( 'Updating translations for %1$s (%2$s)&#8230;' ), $language_item_name, $item->language ) );
+                               break;
+               }
 
 
-       function __construct($args = array()) {
-               parent::__construct($args);
-       }
+               $allow_relaxed_file_ownership = false;
+               if ( 'core' == $type && isset( $item->new_files ) && ! $item->new_files ) {
+                       $allow_relaxed_file_ownership = true;
+               }
 
 
-       function add_strings() {
-               parent::add_strings();
-               $this->upgrader->strings['skin_before_update_header'] = __('Updating Theme %1$s (%2$d/%3$d)');
-       }
+               // Boom, This sites about to get a whole new splash of paint!
+               $upgrade_result = $upgrader->upgrade( $upgrader_item, array(
+                       'clear_update_cache' => false,
+                       // Always use partial builds if possible for core updates.
+                       'pre_check_md5'      => false,
+                       // Only available for core updates.
+                       'attempt_rollback'   => true,
+                       // Allow relaxed file ownership in some scenarios
+                       'allow_relaxed_file_ownership' => $allow_relaxed_file_ownership,
+               ) );
 
 
-       function before() {
-               parent::before( $this->theme_info->display('Name') );
-       }
+               // If the filesystem is unavailable, false is returned.
+               if ( false === $upgrade_result ) {
+                       $upgrade_result = new WP_Error( 'fs_unavailable', __( 'Could not access filesystem.' ) );
+               }
 
 
-       function after() {
-               parent::after( $this->theme_info->display('Name') );
-       }
+               // Core doesn't output this, so let's append it so we don't get confused.
+               if ( 'core' == $type ) {
+                       if ( is_wp_error( $upgrade_result ) ) {
+                               $skin->error( __( 'Installation Failed' ), $upgrade_result );
+                       } else {
+                               $skin->feedback( __( 'WordPress updated successfully' ) );
+                       }
+               }
 
 
-       function bulk_footer() {
-               parent::bulk_footer();
-               $update_actions =  array(
-                       'themes_page' => '<a href="' . self_admin_url('themes.php') . '" title="' . esc_attr__('Go to themes page') . '" target="_parent">' . __('Return to Themes page') . '</a>',
-                       'updates_page' => '<a href="' . self_admin_url('update-core.php') . '" title="' . esc_attr__('Go to WordPress Updates page') . '" target="_parent">' . __('Return to WordPress Updates') . '</a>'
+               $this->update_results[ $type ][] = (object) array(
+                       'item'     => $item,
+                       'result'   => $upgrade_result,
+                       'name'     => $item_name,
+                       'messages' => $skin->get_upgrade_messages()
                );
                );
-               if ( ! current_user_can( 'switch_themes' ) && ! current_user_can( 'edit_theme_options' ) )
-                       unset( $update_actions['themes_page'] );
 
 
-               $update_actions = apply_filters('update_bulk_theme_complete_actions', $update_actions, $this->theme_info );
-               if ( ! empty($update_actions) )
-                       $this->feedback(implode(' | ', (array)$update_actions));
+               return $upgrade_result;
        }
        }
-}
 
 
-/**
- * Plugin Installer Skin for WordPress Plugin Installer.
- *
- * @TODO More Detailed docs, for methods as well.
- *
- * @package WordPress
- * @subpackage Upgrader
- * @since 2.8.0
- */
-class Plugin_Installer_Skin extends WP_Upgrader_Skin {
-       var $api;
-       var $type;
+       /**
+        * Kicks off the background update process, looping through all pending updates.
+        *
+        * @since 3.7.0
+        *
+        * @global wpdb   $wpdb
+        * @global string $wp_version
+        */
+       public function run() {
+               global $wpdb, $wp_version;
 
 
-       function __construct($args = array()) {
-               $defaults = array( 'type' => 'web', 'url' => '', 'plugin' => '', 'nonce' => '', 'title' => '' );
-               $args = wp_parse_args($args, $defaults);
+               if ( $this->is_disabled() )
+                       return;
 
 
-               $this->type = $args['type'];
-               $this->api = isset($args['api']) ? $args['api'] : array();
+               if ( ! is_main_network() || ! is_main_site() )
+                       return;
 
 
-               parent::__construct($args);
-       }
+               $lock_name = 'auto_updater.lock';
 
 
-       function before() {
-               if ( !empty($this->api) )
-                       $this->upgrader->strings['process_success'] = sprintf( __('Successfully installed the plugin <strong>%s %s</strong>.'), $this->api->name, $this->api->version);
-       }
+               // Try to lock
+               $lock_result = $wpdb->query( $wpdb->prepare( "INSERT IGNORE INTO `$wpdb->options` ( `option_name`, `option_value`, `autoload` ) VALUES (%s, %s, 'no') /* LOCK */", $lock_name, time() ) );
 
 
-       function after() {
+               if ( ! $lock_result ) {
+                       $lock_result = get_option( $lock_name );
 
 
-               $plugin_file = $this->upgrader->plugin_info();
+                       // If we couldn't create a lock, and there isn't a lock, bail
+                       if ( ! $lock_result )
+                               return;
 
 
-               $install_actions = array();
-
-               $from = isset($_GET['from']) ? stripslashes($_GET['from']) : 'plugins';
+                       // Check to see if the lock is still valid
+                       if ( $lock_result > ( time() - HOUR_IN_SECONDS ) )
+                               return;
+               }
 
 
-               if ( 'import' == $from )
-                       $install_actions['activate_plugin'] = '<a href="' . wp_nonce_url('plugins.php?action=activate&amp;from=import&amp;plugin=' . $plugin_file, 'activate-plugin_' . $plugin_file) . '" title="' . esc_attr__('Activate this plugin') . '" target="_parent">' . __('Activate Plugin &amp; Run Importer') . '</a>';
-               else
-                       $install_actions['activate_plugin'] = '<a href="' . wp_nonce_url('plugins.php?action=activate&amp;plugin=' . $plugin_file, 'activate-plugin_' . $plugin_file) . '" title="' . esc_attr__('Activate this plugin') . '" target="_parent">' . __('Activate Plugin') . '</a>';
+               // Update the lock, as by this point we've definitely got a lock, just need to fire the actions
+               update_option( $lock_name, time() );
+
+               // Don't automatically run these thins, as we'll handle it ourselves
+               remove_action( 'upgrader_process_complete', array( 'Language_Pack_Upgrader', 'async_upgrade' ), 20 );
+               remove_action( 'upgrader_process_complete', 'wp_version_check' );
+               remove_action( 'upgrader_process_complete', 'wp_update_plugins' );
+               remove_action( 'upgrader_process_complete', 'wp_update_themes' );
+
+               // Next, Plugins
+               wp_update_plugins(); // Check for Plugin updates
+               $plugin_updates = get_site_transient( 'update_plugins' );
+               if ( $plugin_updates && !empty( $plugin_updates->response ) ) {
+                       foreach ( $plugin_updates->response as $plugin ) {
+                               $this->update( 'plugin', $plugin );
+                       }
+                       // Force refresh of plugin update information
+                       wp_clean_plugins_cache();
+               }
 
 
-               if ( is_multisite() && current_user_can( 'manage_network_plugins' ) ) {
-                       $install_actions['network_activate'] = '<a href="' . wp_nonce_url('plugins.php?action=activate&amp;networkwide=1&amp;plugin=' . $plugin_file, 'activate-plugin_' . $plugin_file) . '" title="' . esc_attr__('Activate this plugin for all sites in this network') . '" target="_parent">' . __('Network Activate') . '</a>';
-                       unset( $install_actions['activate_plugin'] );
+               // Next, those themes we all love
+               wp_update_themes();  // Check for Theme updates
+               $theme_updates = get_site_transient( 'update_themes' );
+               if ( $theme_updates && !empty( $theme_updates->response ) ) {
+                       foreach ( $theme_updates->response as $theme ) {
+                               $this->update( 'theme', (object) $theme );
+                       }
+                       // Force refresh of theme update information
+                       wp_clean_themes_cache();
                }
 
                }
 
-               if ( 'import' == $from )
-                       $install_actions['importers_page'] = '<a href="' . admin_url('import.php') . '" title="' . esc_attr__('Return to Importers') . '" target="_parent">' . __('Return to Importers') . '</a>';
-               else if ( $this->type == 'web' )
-                       $install_actions['plugins_page'] = '<a href="' . self_admin_url('plugin-install.php') . '" title="' . esc_attr__('Return to Plugin Installer') . '" target="_parent">' . __('Return to Plugin Installer') . '</a>';
-               else
-                       $install_actions['plugins_page'] = '<a href="' . self_admin_url('plugins.php') . '" title="' . esc_attr__('Return to Plugins page') . '" target="_parent">' . __('Return to Plugins page') . '</a>';
+               // Next, Process any core update
+               wp_version_check(); // Check for Core updates
+               $core_update = find_core_auto_update();
+
+               if ( $core_update )
+                       $this->update( 'core', $core_update );
 
 
-               if ( ! $this->result || is_wp_error($this->result) ) {
-                       unset( $install_actions['activate_plugin'], $install_actions['network_activate'] );
-               } elseif ( ! current_user_can( 'activate_plugins' ) ) {
-                       unset( $install_actions['activate_plugin'] );
+               // Clean up, and check for any pending translations
+               // (Core_Upgrader checks for core updates)
+               $theme_stats = array();
+               if ( isset( $this->update_results['theme'] ) ) {
+                       foreach ( $this->update_results['theme'] as $upgrade ) {
+                               $theme_stats[ $upgrade->item->theme ] = ( true === $upgrade->result );
+                       }
                }
                }
+               wp_update_themes( $theme_stats );  // Check for Theme updates
 
 
-               $install_actions = apply_filters('install_plugin_complete_actions', $install_actions, $this->api, $plugin_file);
-               if ( ! empty($install_actions) )
-                       $this->feedback(implode(' | ', (array)$install_actions));
-       }
-}
+               $plugin_stats = array();
+               if ( isset( $this->update_results['plugin'] ) ) {
+                       foreach ( $this->update_results['plugin'] as $upgrade ) {
+                               $plugin_stats[ $upgrade->item->plugin ] = ( true === $upgrade->result );
+                       }
+               }
+               wp_update_plugins( $plugin_stats ); // Check for Plugin updates
 
 
-/**
- * Theme Installer Skin for the WordPress Theme Installer.
- *
- * @TODO More Detailed docs, for methods as well.
- *
- * @package WordPress
- * @subpackage Upgrader
- * @since 2.8.0
- */
-class Theme_Installer_Skin extends WP_Upgrader_Skin {
-       var $api;
-       var $type;
+               // Finally, Process any new translations
+               $language_updates = wp_get_translation_updates();
+               if ( $language_updates ) {
+                       foreach ( $language_updates as $update ) {
+                               $this->update( 'translation', $update );
+                       }
 
 
-       function __construct($args = array()) {
-               $defaults = array( 'type' => 'web', 'url' => '', 'theme' => '', 'nonce' => '', 'title' => '' );
-               $args = wp_parse_args($args, $defaults);
+                       // Clear existing caches
+                       wp_clean_update_cache();
 
 
-               $this->type = $args['type'];
-               $this->api = isset($args['api']) ? $args['api'] : array();
+                       wp_version_check();  // check for Core updates
+                       wp_update_themes();  // Check for Theme updates
+                       wp_update_plugins(); // Check for Plugin updates
+               }
 
 
-               parent::__construct($args);
-       }
+               // Send debugging email to all development installs.
+               if ( ! empty( $this->update_results ) ) {
+                       $development_version = false !== strpos( $wp_version, '-' );
+
+                       /**
+                        * Filter whether to send a debugging email for each automatic background update.
+                        *
+                        * @since 3.7.0
+                        *
+                        * @param bool $development_version By default, emails are sent if the
+                        *                                  install is a development version.
+                        *                                  Return false to avoid the email.
+                        */
+                       if ( apply_filters( 'automatic_updates_send_debug_email', $development_version ) )
+                               $this->send_debug_email();
+
+                       if ( ! empty( $this->update_results['core'] ) )
+                               $this->after_core_update( $this->update_results['core'][0] );
+
+                       /**
+                        * Fires after all automatic updates have run.
+                        *
+                        * @since 3.8.0
+                        *
+                        * @param array $update_results The results of all attempted updates.
+                        */
+                       do_action( 'automatic_updates_complete', $this->update_results );
+               }
 
 
-       function before() {
-               if ( !empty($this->api) )
-                       $this->upgrader->strings['process_success'] = sprintf( $this->upgrader->strings['process_success_specific'], $this->api->name, $this->api->version);
+               // Clear the lock
+               delete_option( $lock_name );
        }
 
        }
 
-       function after() {
-               if ( empty($this->upgrader->result['destination_name']) )
+       /**
+        * If we tried to perform a core update, check if we should send an email,
+        * and if we need to avoid processing future updates.
+        *
+        * @global string $wp_version
+        *
+        * @param object|WP_Error $update_result The result of the core update. Includes the update offer and result.
+        */
+       protected function after_core_update( $update_result ) {
+               global $wp_version;
+
+               $core_update = $update_result->item;
+               $result      = $update_result->result;
+
+               if ( ! is_wp_error( $result ) ) {
+                       $this->send_email( 'success', $core_update );
                        return;
                        return;
+               }
+
+               $error_code = $result->get_error_code();
+
+               // Any of these WP_Error codes are critical failures, as in they occurred after we started to copy core files.
+               // We should not try to perform a background update again until there is a successful one-click update performed by the user.
+               $critical = false;
+               if ( $error_code === 'disk_full' || false !== strpos( $error_code, '__copy_dir' ) ) {
+                       $critical = true;
+               } elseif ( $error_code === 'rollback_was_required' && is_wp_error( $result->get_error_data()->rollback ) ) {
+                       // A rollback is only critical if it failed too.
+                       $critical = true;
+                       $rollback_result = $result->get_error_data()->rollback;
+               } elseif ( false !== strpos( $error_code, 'do_rollback' ) ) {
+                       $critical = true;
+               }
 
 
-               $theme_info = $this->upgrader->theme_info();
-               if ( empty( $theme_info ) )
+               if ( $critical ) {
+                       $critical_data = array(
+                               'attempted'  => $core_update->current,
+                               'current'    => $wp_version,
+                               'error_code' => $error_code,
+                               'error_data' => $result->get_error_data(),
+                               'timestamp'  => time(),
+                               'critical'   => true,
+                       );
+                       if ( isset( $rollback_result ) ) {
+                               $critical_data['rollback_code'] = $rollback_result->get_error_code();
+                               $critical_data['rollback_data'] = $rollback_result->get_error_data();
+                       }
+                       update_site_option( 'auto_core_update_failed', $critical_data );
+                       $this->send_email( 'critical', $core_update, $result );
                        return;
                        return;
+               }
 
 
-               $name       = $theme_info->display('Name');
-               $stylesheet = $this->upgrader->result['destination_name'];
-               $template   = $theme_info->get_template();
-
-               $preview_link = add_query_arg( array(
-                       'preview'    => 1,
-                       'template'   => urlencode( $template ),
-                       'stylesheet' => urlencode( $stylesheet ),
-               ), trailingslashit( home_url() ) );
-
-               $activate_link = add_query_arg( array(
-                       'action'     => 'activate',
-                       'template'   => urlencode( $template ),
-                       'stylesheet' => urlencode( $stylesheet ),
-               ), admin_url('themes.php') );
-               $activate_link = wp_nonce_url( $activate_link, 'switch-theme_' . $stylesheet );
-
-               $install_actions = array();
-               $install_actions['preview']  = '<a href="' . esc_url( $preview_link ) . '" class="hide-if-customize" title="' . esc_attr( sprintf( __('Preview &#8220;%s&#8221;'), $name ) ) . '">' . __('Preview') . '</a>';
-               $install_actions['preview'] .= '<a href="' . wp_customize_url( $stylesheet ) . '" class="hide-if-no-customize load-customize" title="' . esc_attr( sprintf( __('Preview &#8220;%s&#8221;'), $name ) ) . '">' . __('Live Preview') . '</a>';
-               $install_actions['activate'] = '<a href="' . esc_url( $activate_link ) . '" class="activatelink" title="' . esc_attr( sprintf( __('Activate &#8220;%s&#8221;'), $name ) ) . '">' . __('Activate') . '</a>';
-
-               if ( is_network_admin() && current_user_can( 'manage_network_themes' ) )
-                       $install_actions['network_enable'] = '<a href="' . esc_url( wp_nonce_url( 'themes.php?action=enable&amp;theme=' . urlencode( $stylesheet ), 'enable-theme_' . $stylesheet ) ) . '" title="' . esc_attr__( 'Enable this theme for all sites in this network' ) . '" target="_parent">' . __( 'Network Enable' ) . '</a>';
-
-               if ( $this->type == 'web' )
-                       $install_actions['themes_page'] = '<a href="' . self_admin_url('theme-install.php') . '" title="' . esc_attr__('Return to Theme Installer') . '" target="_parent">' . __('Return to Theme Installer') . '</a>';
-               elseif ( current_user_can( 'switch_themes' ) || current_user_can( 'edit_theme_options' ) )
-                       $install_actions['themes_page'] = '<a href="' . self_admin_url('themes.php') . '" title="' . esc_attr__('Themes page') . '" target="_parent">' . __('Return to Themes page') . '</a>';
-
-               if ( ! $this->result || is_wp_error($this->result) || is_network_admin() || ! current_user_can( 'switch_themes' ) )
-                       unset( $install_actions['activate'], $install_actions['preview'] );
-
-               $install_actions = apply_filters('install_theme_complete_actions', $install_actions, $this->api, $stylesheet, $theme_info);
-               if ( ! empty($install_actions) )
-                       $this->feedback(implode(' | ', (array)$install_actions));
-       }
-}
+               /*
+                * Any other WP_Error code (like download_failed or files_not_writable) occurs before
+                * we tried to copy over core files. Thus, the failures are early and graceful.
+                *
+                * We should avoid trying to perform a background update again for the same version.
+                * But we can try again if another version is released.
+                *
+                * For certain 'transient' failures, like download_failed, we should allow retries.
+                * In fact, let's schedule a special update for an hour from now. (It's possible
+                * the issue could actually be on WordPress.org's side.) If that one fails, then email.
+                */
+               $send = true;
+               $transient_failures = array( 'incompatible_archive', 'download_failed', 'insane_distro' );
+               if ( in_array( $error_code, $transient_failures ) && ! get_site_option( 'auto_core_update_failed' ) ) {
+                       wp_schedule_single_event( time() + HOUR_IN_SECONDS, 'wp_maybe_auto_update' );
+                       $send = false;
+               }
+
+               $n = get_site_option( 'auto_core_update_notified' );
+               // Don't notify if we've already notified the same email address of the same version of the same notification type.
+               if ( $n && 'fail' == $n['type'] && $n['email'] == get_site_option( 'admin_email' ) && $n['version'] == $core_update->current )
+                       $send = false;
+
+               update_site_option( 'auto_core_update_failed', array(
+                       'attempted'  => $core_update->current,
+                       'current'    => $wp_version,
+                       'error_code' => $error_code,
+                       'error_data' => $result->get_error_data(),
+                       'timestamp'  => time(),
+                       'retry'      => in_array( $error_code, $transient_failures ),
+               ) );
 
 
-/**
- * Theme Upgrader Skin for WordPress Theme Upgrades.
- *
- * @TODO More Detailed docs, for methods as well.
- *
- * @package WordPress
- * @subpackage Upgrader
- * @since 2.8.0
- */
-class Theme_Upgrader_Skin extends WP_Upgrader_Skin {
-       var $theme = '';
+               if ( $send )
+                       $this->send_email( 'fail', $core_update, $result );
+       }
+
+       /**
+        * Sends an email upon the completion or failure of a background core update.
+        *
+        * @since 3.7.0
+        *
+        * @global string $wp_version
+        *
+        * @param string $type        The type of email to send. Can be one of 'success', 'fail', 'manual', 'critical'.
+        * @param object $core_update The update offer that was attempted.
+        * @param mixed  $result      Optional. The result for the core update. Can be WP_Error.
+        */
+       protected function send_email( $type, $core_update, $result = null ) {
+               update_site_option( 'auto_core_update_notified', array(
+                       'type'      => $type,
+                       'email'     => get_site_option( 'admin_email' ),
+                       'version'   => $core_update->current,
+                       'timestamp' => time(),
+               ) );
 
 
-       function __construct($args = array()) {
-               $defaults = array( 'url' => '', 'theme' => '', 'nonce' => '', 'title' => __('Update Theme') );
-               $args = wp_parse_args($args, $defaults);
+               $next_user_core_update = get_preferred_from_update_core();
+               // If the update transient is empty, use the update we just performed
+               if ( ! $next_user_core_update )
+                       $next_user_core_update = $core_update;
+               $newer_version_available = ( 'upgrade' == $next_user_core_update->response && version_compare( $next_user_core_update->version, $core_update->version, '>' ) );
+
+               /**
+                * Filter whether to send an email following an automatic background core update.
+                *
+                * @since 3.7.0
+                *
+                * @param bool   $send        Whether to send the email. Default true.
+                * @param string $type        The type of email to send. Can be one of
+                *                            'success', 'fail', 'critical'.
+                * @param object $core_update The update offer that was attempted.
+                * @param mixed  $result      The result for the core update. Can be WP_Error.
+                */
+               if ( 'manual' !== $type && ! apply_filters( 'auto_core_update_send_email', true, $type, $core_update, $result ) )
+                       return;
 
 
-               $this->theme = $args['theme'];
+               switch ( $type ) {
+                       case 'success' : // We updated.
+                               /* translators: 1: Site name, 2: WordPress version number. */
+                               $subject = __( '[%1$s] Your site has updated to WordPress %2$s' );
+                               break;
 
 
-               parent::__construct($args);
-       }
+                       case 'fail' :   // We tried to update but couldn't.
+                       case 'manual' : // We can't update (and made no attempt).
+                               /* translators: 1: Site name, 2: WordPress version number. */
+                               $subject = __( '[%1$s] WordPress %2$s is available. Please update!' );
+                               break;
 
 
-       function after() {
-
-               $update_actions = array();
-               if ( ! empty( $this->upgrader->result['destination_name'] ) && $theme_info = $this->upgrader->theme_info() ) {
-                       $name       = $theme_info->display('Name');
-                       $stylesheet = $this->upgrader->result['destination_name'];
-                       $template   = $theme_info->get_template();
-
-                       $preview_link = add_query_arg( array(
-                               'preview'    => 1,
-                               'template'   => urlencode( $template ),
-                               'stylesheet' => urlencode( $stylesheet ),
-                       ), trailingslashit( home_url() ) );
-
-                       $activate_link = add_query_arg( array(
-                               'action'     => 'activate',
-                               'template'   => urlencode( $template ),
-                               'stylesheet' => urlencode( $stylesheet ),
-                       ), admin_url('themes.php') );
-                       $activate_link = wp_nonce_url( $activate_link, 'switch-theme_' . $stylesheet );
-
-                       if ( get_stylesheet() == $stylesheet ) {
-                               if ( current_user_can( 'edit_theme_options' ) )
-                                       $update_actions['preview']  = '<a href="' . wp_customize_url( $stylesheet ) . '" class="hide-if-no-customize load-customize" title="' . esc_attr( sprintf( __('Customize &#8220;%s&#8221;'), $name ) ) . '">' . __('Customize') . '</a>';
-                       } elseif ( current_user_can( 'switch_themes' ) ) {
-                               $update_actions['preview']  = '<a href="' . esc_url( $preview_link ) . '" class="hide-if-customize" title="' . esc_attr( sprintf( __('Preview &#8220;%s&#8221;'), $name ) ) . '">' . __('Preview') . '</a>';
-                               $update_actions['preview'] .= '<a href="' . wp_customize_url( $stylesheet ) . '" class="hide-if-no-customize load-customize" title="' . esc_attr( sprintf( __('Preview &#8220;%s&#8221;'), $name ) ) . '">' . __('Live Preview') . '</a>';
-                               $update_actions['activate'] = '<a href="' . esc_url( $activate_link ) . '" class="activatelink" title="' . esc_attr( sprintf( __('Activate &#8220;%s&#8221;'), $name ) ) . '">' . __('Activate') . '</a>';
-                       }
+                       case 'critical' : // We tried to update, started to copy files, then things went wrong.
+                               /* translators: 1: Site name. */
+                               $subject = __( '[%1$s] URGENT: Your site may be down due to a failed update' );
+                               break;
 
 
-                       if ( ! $this->result || is_wp_error( $this->result ) || is_network_admin() )
-                               unset( $update_actions['preview'], $update_actions['activate'] );
+                       default :
+                               return;
                }
 
                }
 
-               $update_actions['themes_page'] = '<a href="' . self_admin_url('themes.php') . '" title="' . esc_attr__('Return to Themes page') . '" target="_parent">' . __('Return to Themes page') . '</a>';
+               // If the auto update is not to the latest version, say that the current version of WP is available instead.
+               $version = 'success' === $type ? $core_update->current : $next_user_core_update->current;
+               $subject = sprintf( $subject, wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ), $version );
 
 
-               $update_actions = apply_filters('update_theme_complete_actions', $update_actions, $this->theme);
-               if ( ! empty($update_actions) )
-                       $this->feedback(implode(' | ', (array)$update_actions));
-       }
-}
+               $body = '';
 
 
-/**
- * Upgrade Skin helper for File uploads. This class handles the upload process and passes it as if its a local file to the Upgrade/Installer functions.
- *
- * @TODO More Detailed docs, for methods as well.
- *
- * @package WordPress
- * @subpackage Upgrader
- * @since 2.8.0
- */
-class File_Upload_Upgrader {
-       var $package;
-       var $filename;
-       var $id = 0;
+               switch ( $type ) {
+                       case 'success' :
+                               $body .= sprintf( __( 'Howdy! Your site at %1$s has been updated automatically to WordPress %2$s.' ), home_url(), $core_update->current );
+                               $body .= "\n\n";
+                               if ( ! $newer_version_available )
+                                       $body .= __( 'No further action is needed on your part.' ) . ' ';
 
 
-       function __construct($form, $urlholder) {
+                               // Can only reference the About screen if their update was successful.
+                               list( $about_version ) = explode( '-', $core_update->current, 2 );
+                               $body .= sprintf( __( "For more on version %s, see the About WordPress screen:" ), $about_version );
+                               $body .= "\n" . admin_url( 'about.php' );
 
 
-               if ( empty($_FILES[$form]['name']) && empty($_GET[$urlholder]) )
-                       wp_die(__('Please select a file'));
+                               if ( $newer_version_available ) {
+                                       $body .= "\n\n" . sprintf( __( 'WordPress %s is also now available.' ), $next_user_core_update->current ) . ' ';
+                                       $body .= __( 'Updating is easy and only takes a few moments:' );
+                                       $body .= "\n" . network_admin_url( 'update-core.php' );
+                               }
 
 
-               //Handle a newly uploaded file, Else assume its already been uploaded
-               if ( ! empty($_FILES) ) {
-                       $overrides = array( 'test_form' => false, 'test_type' => false );
-                       $file = wp_handle_upload( $_FILES[$form], $overrides );
+                               break;
 
 
-                       if ( isset( $file['error'] ) )
-                               wp_die( $file['error'] );
+                       case 'fail' :
+                       case 'manual' :
+                               $body .= sprintf( __( 'Please update your site at %1$s to WordPress %2$s.' ), home_url(), $next_user_core_update->current );
 
 
-                       $this->filename = $_FILES[$form]['name'];
-                       $this->package = $file['file'];
+                               $body .= "\n\n";
 
 
-                       // Construct the object array
-                       $object = array(
-                               'post_title' => $this->filename,
-                               'post_content' => $file['url'],
-                               'post_mime_type' => $file['type'],
-                               'guid' => $file['url'],
-                               'context' => 'upgrader',
-                               'post_status' => 'private'
-                       );
+                               // Don't show this message if there is a newer version available.
+                               // Potential for confusion, and also not useful for them to know at this point.
+                               if ( 'fail' == $type && ! $newer_version_available )
+                                       $body .= __( 'We tried but were unable to update your site automatically.' ) . ' ';
 
 
-                       // Save the data
-                       $this->id = wp_insert_attachment( $object, $file['file'] );
+                               $body .= __( 'Updating is easy and only takes a few moments:' );
+                               $body .= "\n" . network_admin_url( 'update-core.php' );
+                               break;
 
 
-                       // schedule a cleanup for 2 hours from now in case of failed install
-                       wp_schedule_single_event( time() + 7200, 'upgrader_scheduled_cleanup', array( $this->id ) );
+                       case 'critical' :
+                               if ( $newer_version_available )
+                                       $body .= sprintf( __( 'Your site at %1$s experienced a critical failure while trying to update WordPress to version %2$s.' ), home_url(), $core_update->current );
+                               else
+                                       $body .= sprintf( __( 'Your site at %1$s experienced a critical failure while trying to update to the latest version of WordPress, %2$s.' ), home_url(), $core_update->current );
 
 
-               } elseif ( is_numeric( $_GET[$urlholder] ) ) {
-                       // Numeric Package = previously uploaded file, see above.
-                       $this->id = (int) $_GET[$urlholder];
-                       $attachment = get_post( $this->id );
-                       if ( empty($attachment) )
-                               wp_die(__('Please select a file'));
+                               $body .= "\n\n" . __( "This means your site may be offline or broken. Don't panic; this can be fixed." );
 
 
-                       $this->filename = $attachment->post_title;
-                       $this->package = get_attached_file( $attachment->ID );
+                               $body .= "\n\n" . __( "Please check out your site now. It's possible that everything is working. If it says you need to update, you should do so:" );
+                               $body .= "\n" . network_admin_url( 'update-core.php' );
+                               break;
+               }
+
+               $critical_support = 'critical' === $type && ! empty( $core_update->support_email );
+               if ( $critical_support ) {
+                       // Support offer if available.
+                       $body .= "\n\n" . sprintf( __( "The WordPress team is willing to help you. Forward this email to %s and the team will work with you to make sure your site is working." ), $core_update->support_email );
                } else {
                } else {
-                       // Else, It's set to something, Back compat for plugins using the old (pre-3.3) File_Uploader handler.
-                       if ( ! ( ( $uploads = wp_upload_dir() ) && false === $uploads['error'] ) )
-                               wp_die( $uploads['error'] );
+                       // Add a note about the support forums.
+                       $body .= "\n\n" . __( 'If you experience any issues or need support, the volunteers in the WordPress.org support forums may be able to help.' );
+                       $body .= "\n" . __( 'https://wordpress.org/support/' );
+               }
 
 
-                       $this->filename = $_GET[$urlholder];
-                       $this->package = $uploads['basedir'] . '/' . $this->filename;
+               // Updates are important!
+               if ( $type != 'success' || $newer_version_available ) {
+                       $body .= "\n\n" . __( 'Keeping your site updated is important for security. It also makes the internet a safer place for you and your readers.' );
                }
                }
-       }
 
 
-       function cleanup() {
-               if ( $this->id )
-                       wp_delete_attachment( $this->id );
+               if ( $critical_support ) {
+                       $body .= " " . __( "If you reach out to us, we'll also ensure you'll never have this problem again." );
+               }
 
 
-               elseif ( file_exists( $this->package ) )
-                       return @unlink( $this->package );
+               // If things are successful and we're now on the latest, mention plugins and themes if any are out of date.
+               if ( $type == 'success' && ! $newer_version_available && ( get_plugin_updates() || get_theme_updates() ) ) {
+                       $body .= "\n\n" . __( 'You also have some plugins or themes with updates available. Update them now:' );
+                       $body .= "\n" . network_admin_url();
+               }
 
 
-               return true;
+               $body .= "\n\n" . __( 'The WordPress Team' ) . "\n";
+
+               if ( 'critical' == $type && is_wp_error( $result ) ) {
+                       $body .= "\n***\n\n";
+                       $body .= sprintf( __( 'Your site was running version %s.' ), $GLOBALS['wp_version'] );
+                       $body .= ' ' . __( 'We have some data that describes the error your site encountered.' );
+                       $body .= ' ' . __( 'Your hosting company, support forum volunteers, or a friendly developer may be able to use this information to help you:' );
+
+                       // If we had a rollback and we're still critical, then the rollback failed too.
+                       // Loop through all errors (the main WP_Error, the update result, the rollback result) for code, data, etc.
+                       if ( 'rollback_was_required' == $result->get_error_code() )
+                               $errors = array( $result, $result->get_error_data()->update, $result->get_error_data()->rollback );
+                       else
+                               $errors = array( $result );
+
+                       foreach ( $errors as $error ) {
+                               if ( ! is_wp_error( $error ) )
+                                       continue;
+                               $error_code = $error->get_error_code();
+                               $body .= "\n\n" . sprintf( __( "Error code: %s" ), $error_code );
+                               if ( 'rollback_was_required' == $error_code )
+                                       continue;
+                               if ( $error->get_error_message() )
+                                       $body .= "\n" . $error->get_error_message();
+                               $error_data = $error->get_error_data();
+                               if ( $error_data )
+                                       $body .= "\n" . implode( ', ', (array) $error_data );
+                       }
+                       $body .= "\n";
+               }
+
+               $to  = get_site_option( 'admin_email' );
+               $headers = '';
+
+               $email = compact( 'to', 'subject', 'body', 'headers' );
+
+               /**
+                * Filter the email sent following an automatic background core update.
+                *
+                * @since 3.7.0
+                *
+                * @param array $email {
+                *     Array of email arguments that will be passed to wp_mail().
+                *
+                *     @type string $to      The email recipient. An array of emails
+                *                            can be returned, as handled by wp_mail().
+                *     @type string $subject The email's subject.
+                *     @type string $body    The email message body.
+                *     @type string $headers Any email headers, defaults to no headers.
+                * }
+                * @param string $type        The type of email being sent. Can be one of
+                *                            'success', 'fail', 'manual', 'critical'.
+                * @param object $core_update The update offer that was attempted.
+                * @param mixed  $result      The result for the core update. Can be WP_Error.
+                */
+               $email = apply_filters( 'auto_core_update_email', $email, $type, $core_update, $result );
+
+               wp_mail( $email['to'], wp_specialchars_decode( $email['subject'] ), $email['body'], $email['headers'] );
+       }
+
+       /**
+        * Prepares and sends an email of a full log of background update results, useful for debugging and geekery.
+        *
+        * @since 3.7.0
+        */
+       protected function send_debug_email() {
+               $update_count = 0;
+               foreach ( $this->update_results as $type => $updates )
+                       $update_count += count( $updates );
+
+               $body = array();
+               $failures = 0;
+
+               $body[] = sprintf( __( 'WordPress site: %s' ), network_home_url( '/' ) );
+
+               // Core
+               if ( isset( $this->update_results['core'] ) ) {
+                       $result = $this->update_results['core'][0];
+                       if ( $result->result && ! is_wp_error( $result->result ) ) {
+                               $body[] = sprintf( __( 'SUCCESS: WordPress was successfully updated to %s' ), $result->name );
+                       } else {
+                               $body[] = sprintf( __( 'FAILED: WordPress failed to update to %s' ), $result->name );
+                               $failures++;
+                       }
+                       $body[] = '';
+               }
+
+               // Plugins, Themes, Translations
+               foreach ( array( 'plugin', 'theme', 'translation' ) as $type ) {
+                       if ( ! isset( $this->update_results[ $type ] ) )
+                               continue;
+                       $success_items = wp_list_filter( $this->update_results[ $type ], array( 'result' => true ) );
+                       if ( $success_items ) {
+                               $messages = array(
+                                       'plugin'      => __( 'The following plugins were successfully updated:' ),
+                                       'theme'       => __( 'The following themes were successfully updated:' ),
+                                       'translation' => __( 'The following translations were successfully updated:' ),
+                               );
+
+                               $body[] = $messages[ $type ];
+                               foreach ( wp_list_pluck( $success_items, 'name' ) as $name ) {
+                                       $body[] = ' * ' . sprintf( __( 'SUCCESS: %s' ), $name );
+                               }
+                       }
+                       if ( $success_items != $this->update_results[ $type ] ) {
+                               // Failed updates
+                               $messages = array(
+                                       'plugin'      => __( 'The following plugins failed to update:' ),
+                                       'theme'       => __( 'The following themes failed to update:' ),
+                                       'translation' => __( 'The following translations failed to update:' ),
+                               );
+
+                               $body[] = $messages[ $type ];
+                               foreach ( $this->update_results[ $type ] as $item ) {
+                                       if ( ! $item->result || is_wp_error( $item->result ) ) {
+                                               $body[] = ' * ' . sprintf( __( 'FAILED: %s' ), $item->name );
+                                               $failures++;
+                                       }
+                               }
+                       }
+                       $body[] = '';
+               }
+
+               $site_title = wp_specialchars_decode( get_bloginfo( 'name' ), ENT_QUOTES );
+               if ( $failures ) {
+                       $body[] = trim( __(
+"BETA TESTING?
+=============
+
+This debugging email is sent when you are using a development version of WordPress.
+
+If you think these failures might be due to a bug in WordPress, could you report it?
+ * Open a thread in the support forums: https://wordpress.org/support/forum/alphabeta
+ * Or, if you're comfortable writing a bug report: https://core.trac.wordpress.org/
+
+Thanks! -- The WordPress Team" ) );
+                       $body[] = '';
+
+                       $subject = sprintf( __( '[%s] There were failures during background updates' ), $site_title );
+               } else {
+                       $subject = sprintf( __( '[%s] Background updates have finished' ), $site_title );
+               }
+
+               $body[] = trim( __(
+'UPDATE LOG
+==========' ) );
+               $body[] = '';
+
+               foreach ( array( 'core', 'plugin', 'theme', 'translation' ) as $type ) {
+                       if ( ! isset( $this->update_results[ $type ] ) )
+                               continue;
+                       foreach ( $this->update_results[ $type ] as $update ) {
+                               $body[] = $update->name;
+                               $body[] = str_repeat( '-', strlen( $update->name ) );
+                               foreach ( $update->messages as $message )
+                                       $body[] = "  " . html_entity_decode( str_replace( '&#8230;', '...', $message ) );
+                               if ( is_wp_error( $update->result ) ) {
+                                       $results = array( 'update' => $update->result );
+                                       // If we rolled back, we want to know an error that occurred then too.
+                                       if ( 'rollback_was_required' === $update->result->get_error_code() )
+                                               $results = (array) $update->result->get_error_data();
+                                       foreach ( $results as $result_type => $result ) {
+                                               if ( ! is_wp_error( $result ) )
+                                                       continue;
+
+                                               if ( 'rollback' === $result_type ) {
+                                                       /* translators: 1: Error code, 2: Error message. */
+                                                       $body[] = '  ' . sprintf( __( 'Rollback Error: [%1$s] %2$s' ), $result->get_error_code(), $result->get_error_message() );
+                                               } else {
+                                                       /* translators: 1: Error code, 2: Error message. */
+                                                       $body[] = '  ' . sprintf( __( 'Error: [%1$s] %2$s' ), $result->get_error_code(), $result->get_error_message() );
+                                               }
+
+                                               if ( $result->get_error_data() )
+                                                       $body[] = '         ' . implode( ', ', (array) $result->get_error_data() );
+                                       }
+                               }
+                               $body[] = '';
+                       }
+               }
+
+               $email = array(
+                       'to'      => get_site_option( 'admin_email' ),
+                       'subject' => $subject,
+                       'body'    => implode( "\n", $body ),
+                       'headers' => ''
+               );
+
+               /**
+                * Filter the debug email that can be sent following an automatic
+                * background core update.
+                *
+                * @since 3.8.0
+                *
+                * @param array $email {
+                *     Array of email arguments that will be passed to wp_mail().
+                *
+                *     @type string $to      The email recipient. An array of emails
+                *                           can be returned, as handled by wp_mail().
+                *     @type string $subject Email subject.
+                *     @type string $body    Email message body.
+                *     @type string $headers Any email headers. Default empty.
+                * }
+                * @param int   $failures The number of failures encountered while upgrading.
+                * @param mixed $results  The results of all attempted updates.
+                */
+               $email = apply_filters( 'automatic_updates_debug_email', $email, $failures, $this->update_results );
+
+               wp_mail( $email['to'], wp_specialchars_decode( $email['subject'] ), $email['body'], $email['headers'] );
        }
        }
-}
\ No newline at end of file
+}