]> scripts.mit.edu Git - wizard.git/blobdiff - wizard/deploy.py
Convert ad hoc shell calls to singleton instance; fix upgrade bug.
[wizard.git] / wizard / deploy.py
index 48393707c1f5098d9f5e54ff996d541e02d82157..67c4118e0b7c37741a97e5ad7658bdde62b6014a 100644 (file)
@@ -1,30 +1,58 @@
+"""
+Object model for querying information and manipulating deployments
+of autoinstalls.  Every :class:`Deployment` has an :class:`app.ApplicationVersion`
+which in turn has an :class:`app.Application`.
+"""
+
 import os.path
 import fileinput
-import dateutil.parser
-import distutils.version
+import logging
+import decorator
+import datetime
 import tempfile
+import time
+import traceback
+import shutil
+import errno
 
 import wizard
-from wizard import log
+from wizard import app, git, old_log, scripts, shell, sql, util
 
 ## -- Global Functions --
 
-def getInstallLines(vs):
-    """Retrieves a list of lines from the version directory that
-    can be passed to Deployment.parse()"""
-    if os.path.isfile(vs):
-        return fileinput.input([vs])
-    return fileinput.input([vs + "/" + f for f in os.listdir(vs)])
-
-def parse_install_lines(show, options, yield_errors = False):
-    if not show: show = applications()
-    show = frozenset(show)
-    for line in getInstallLines(options.versions_path):
+def get_install_lines(versions_store, user=None):
+    """
+    Low level function that retrieves a list of lines from the
+    :term:`versions store` that can be passed to :meth:`Deployment.parse`.
+    """
+    if os.path.isfile(versions_store):
+        return fileinput.input([versions_store])
+    if user:
+        return fileinput.input([versions_store + "/" + user])
+    return fileinput.input([versions_store + "/" + f for f in sorted(os.listdir(versions_store))])
+
+def parse_install_lines(show, versions_store, yield_errors = False, user = None):
+    """
+    Generator function for iterating through all autoinstalls.
+    Each item is an instance of :class:`Deployment`, or possibly
+    a :class:`wizard.deploy.Error` if ``yield_errors`` is ``True``.  You can
+    filter out applications and versions by specifying ``app``
+    or ``app-1.2.3`` in ``show``.  This function may generate
+    log output.
+    """
+    if not show:
+        show = app.applications()
+    elif isinstance(show, str):
+        # otherwise, frozenset will treat string as an iterable
+        show = frozenset([show])
+    else:
+        show = frozenset(show)
+    for line in get_install_lines(versions_store, user):
         # construction
         try:
             d = Deployment.parse(line)
             name = d.application.name
-        except NoSuchApplication as e:
+        except app.NoSuchApplication as e:
             if yield_errors:
                 yield e
             continue
@@ -42,209 +70,372 @@ def parse_install_lines(show, options, yield_errors = False):
 
 ## -- Model Objects --
 
+@decorator.decorator
+def chdir_to_location(f, self, *args, **kwargs):
+    """
+    Decorator for making a function have working directory
+    :attr:`Deployment.location`.
+    """
+    with util.ChangeDirectory(self.location):
+        return f(self, *args, **kwargs)
+
 class Deployment(object):
-    """Represents a deployment of an autoinstall; i.e. a concrete
-    directory in web_scripts that has .scripts-version in it."""
+    """
+    Represents a deployment of an autoinstall, e.g. directory
+    that has ``.scripts`` directory or ``.scripts-version``
+    file in it.  Supply ``version`` with an :class:`ApplicationVersion` only if
+    you were reading from the :term:`versions store` and care about
+    speed (data from there can be stale).
+
+    The Deployment interface is somewhat neutered, so you may
+    want to use :class:`WorkingCopy` or :class:`ProductionCopy` for
+    more powerful operations.
+    """
+    #: Absolute path to the deployment
+    location = None
     def __init__(self, location, version=None):
-        """ `location`  Location of the deployment
-            `version`   ApplicationVersion of the app.  ONLY supply this
-                        if you don't mind having stale data; generally
-                        'wizard list' and commands that operate of of the
-                        versions store will set this."""
-        self.location = os.path.realpath(location)
+        self.location = os.path.abspath(location)
         self._app_version = version
         # some cache variables
         self._read_cache = {}
-        self._log = None
+        self._old_log = None
+        self._dsn = None
+        self._url = None
+    def invalidateCache(self):
+        """
+        Invalidates all cached variables.  This currently applies to
+        :attr:`app_version`, :attr:`old_log` and :meth:`read`.
+        """
+        self._app_version = None
+        self._read_cache = {}
+        self._old_log = None
     def read(self, file, force = False):
-        """Reads a file's contents, possibly from cache unless force is True."""
+        """
+        Reads a file's contents, possibly from cache unless ``force``
+        is ``True``.
+        """
         if force or file not in self._read_cache:
             f = open(os.path.join(self.location, file))
             self._read_cache[file] = f.read()
             f.close()
         return self._read_cache[file]
     def extract(self):
-        """Extracts all the values of all variables from deployment."""
+        """
+        Extracts all the values of all variables from deployment.
+        These variables may be used for parametrizing generic parent
+        commits and include things such as database access credentials
+        and local configuration.
+        """
         return self.application.extract(self)
-    def parametrize(self, dir):
-        """Edits files in dir to replace WIZARD_* variables with literal
-        instances.  This is used for constructing virtual merge bases, and
-        as such dir will generally not equal self.location."""
-        return self.application.parametrize(self, dir)
-    def updateVersion(self, version):
-        """Bump the version of this deployment.
-
-        This method will update the version of this deployment in memory
-        and on disk.  It doesn't actually do an upgrade.  The version
-        string you pass here should probably have '-scripts' as a suffix."""
-        self._app_version = self.application.makeVersion(version)
-        f = open(os.path.join(self.scripts_dir, 'version'), 'w')
-        f.write(self.application.name + '-' + version + "\n")
-        f.close()
-    def scriptsifyVersion(self):
-        """Converts from v1.0 to v1.0-scripts; use at end of migration."""
-        self.updateVersion(str(self.version) + '-scripts')
+
+    def verify(self):
+        """
+        Checks if this is an autoinstall, throws an exception if there
+        are problems.
+        """
+        with util.ChangeDirectory(self.location):
+            has_git = os.path.isdir(".git")
+            has_scripts = os.path.isdir(".scripts")
+            if not has_git and has_scripts:
+                raise CorruptedAutoinstallError(self.location)
+            elif has_git and not has_scripts:
+                raise AlreadyVersionedError(self.location)
+            elif not has_git and not has_scripts:
+                if os.path.isfile(".scripts-version"):
+                    raise NotMigratedError(self.location)
+
+    def verifyTag(self, srv_path):
+        """
+        Checks if the purported version has a corresponding tag
+        in the upstream repository.
+        """
+        repo = self.application.repository(srv_path)
+        try:
+            shell.eval("git", "--git-dir", repo, "rev-parse", self.app_version.scripts_tag, '--')
+        except shell.CallError:
+            raise NoTagError(self.app_version.scripts_tag)
+
+    def verifyGit(self, srv_path):
+        """
+        Checks if the autoinstall's Git repository makes sense,
+        checking if the tag is parseable and corresponds to
+        a real application, and if the tag in this repository
+        corresponds to the one in the remote repository.
+        """
+        with util.ChangeDirectory(self.location):
+            repo = self.application.repository(srv_path)
+            def repo_rev_parse(tag):
+                return shell.eval("git", "--git-dir", repo, "rev-parse", tag)
+            def self_rev_parse(tag):
+                try:
+                    return shell.safeCall("git", "rev-parse", tag, strip=True)
+                except shell.CallError:
+                    raise NoLocalTagError(tag)
+            def compare_tags(tag):
+                return repo_rev_parse(tag) == self_rev_parse(tag)
+            if not compare_tags(self.app_version.pristine_tag):
+                raise InconsistentPristineTagError(self.app_version.pristine_tag)
+            if not compare_tags(self.app_version.scripts_tag):
+                raise InconsistentScriptsTagError(self.app_version.scripts_tag)
+            parent = repo_rev_parse(self.app_version.scripts_tag)
+            merge_base = shell.safeCall("git", "merge-base", parent, "HEAD", strip=True)
+            if merge_base != parent:
+                raise HeadNotDescendantError(self.app_version.scripts_tag)
+
+    def verifyConfigured(self):
+        """
+        Checks if the autoinstall is configured running.
+        """
+        if not self.configured:
+            raise NotConfiguredError(self.location)
+
+    @chdir_to_location
+    def verifyVersion(self):
+        """
+        Checks if our version and the version number recorded in a file
+        are consistent.
+        """
+        real = self.application.detectVersion(self)
+        if not real:
+            raise VersionDetectionError
+        elif not str(real) == self.app_version.pristine_tag.partition('-')[2]:
+            raise VersionMismatchError(real, self.version)
+
+    @property
+    @chdir_to_location
+    def configured(self):
+        """Whether or not an autoinstall has been configured/installed for use."""
+        return self.application.checkConfig(self)
+    @property
+    def migrated(self):
+        """Whether or not the autoinstalls has been migrated."""
+        return os.path.isdir(self.scripts_dir)
     @property
     def scripts_dir(self):
+        """The absolute path of the ``.scripts`` directory."""
         return os.path.join(self.location, '.scripts')
     @property
     def old_version_file(self):
-        """Use of this is discouraged for migrated installs."""
-        if os.path.isdir(self.scripts_dir):
-            return os.path.join(self.scripts_dir, 'old-version')
-        else:
-            return os.path.join(self.location, '.scripts-version')
+        """
+        The absolute path of either ``.scripts-version`` (for unmigrated
+        installs) or ``.scripts/version``.
+
+        .. note::
+
+            Use of this is discouraged for migrated installs.
+        """
+        return os.path.join(self.location, '.scripts-version')
     @property
     def version_file(self):
+        """The absolute path of the ``.scripts/version`` file."""
         return os.path.join(self.scripts_dir, 'version')
     @property
+    def dsn_file(self):
+        """The absolute path of the :file:`.scripts/dsn` override file."""
+        return os.path.join(self.scripts_dir, 'dsn')
+    @property
+    def url_file(self):
+        """The absolute path of the :file:`.scripts/url` override file."""
+        return os.path.join(self.scripts_dir, 'url')
+    @property
     def application(self):
+        """The :class:`app.Application` of this deployment."""
         return self.app_version.application
     @property
-    def log(self):
-        if not self._log:
-            self._log = log.DeployLog.load(self)
-        return self._log
+    def old_log(self):
+        """
+        The :class:`wizard.old_log.Log` of this deployment.  This
+        is only applicable to un-migrated autoinstalls.
+        """
+        if not self._old_log:
+            self._old_log = old_log.DeployLog.load(self)
+        return self._old_log
     @property
     def version(self):
-        """Returns the distutils Version of the deployment"""
+        """
+        The :class:`distutils.version.LooseVersion` of this
+        deployment.
+        """
         return self.app_version.version
     @property
     def app_version(self):
-        """Returns the ApplicationVersion of the deployment"""
+        """The :class:`app.ApplicationVersion` of this deployment."""
+        if not self._app_version:
+            if os.path.isdir(os.path.join(self.location, ".git")):
+                try:
+                    with util.ChangeDirectory(self.location):
+                        appname, _, version = git.describe().partition('-')
+                    self._app_version = app.ApplicationVersion.make(appname, version)
+                except shell.CallError:
+                    pass
+        if not self._app_version:
+            try:
+                self._app_version = self.old_log[-1].version
+            except old_log.ScriptsVersionNoSuchFile:
+                pass
         if not self._app_version:
-            if os.path.isfile(self.version_file):
-                fh = open(self.version_file)
-                appname, _, version = fh.read().rstrip().partition('-')
-                fh.close()
-                self._app_version = ApplicationVersion.make(appname, version)
-            else:
-                self._app_version = self.log[-1].version
+            appname = shell.eval("git", "config", "remote.origin.url").rpartition("/")[2].partition(".")[0]
+            self._app_version = app.ApplicationVersion.make(appname, "unknown")
         return self._app_version
+    @property
+    def dsn(self):
+        """The :class:`sqlalchemy.engine.url.URL` for this deployment."""
+        if not self._dsn:
+            self._dsn = sql.fill_url(self.application.dsn(self))
+        return self._dsn
+    @property
+    def url(self):
+        """The :class:`urlparse.ParseResult` for this deployment."""
+        if not self._url:
+            self._url = scripts.fill_url(self.location, self.application.url(self))
+        if not self._url:
+            raise UnknownWebPath
+        return self._url
     @staticmethod
     def parse(line):
-        """Parses a line from the versions directory.
+        """
+        Parses a line from the :term:`versions store`.
 
-        Note: Use this method only when speed is of the utmost
-        importance.  You should prefer to directly create a deployment
-        using Deployment(location) when accuracy is desired."""
+        .. note::
+
+            Use this method only when speed is of the utmost
+            importance.  You should prefer to directly create a deployment
+            with only a ``location`` when possible.
+        """
         line = line.rstrip()
         try:
             location, deploydir = line.split(":")
         except ValueError:
-            return Deployment(line) # lazy loaded version
+            return ProductionCopy(line) # lazy loaded version
         try:
-            return Deployment(location, version=ApplicationVersion.parse(deploydir))
+            return ProductionCopy(location, version=app.ApplicationVersion.parse(deploydir))
         except Error as e:
             e.location = location
             raise e
 
-class Application(object):
-    """Represents the generic notion of an application, i.e.
-    mediawiki or phpbb."""
-    parametrized_files = []
-    def __init__(self, name):
-        self.name = name
-        self.versions = {}
-        # cache variables
-        self._extractors = {}
-        self._parametrizers = {}
-    @property
-    def repository(self):
-        """Returns the Git repository that would contain this application."""
-        repo = os.path.join("/afs/athena.mit.edu/contrib/scripts/git/autoinstalls", self.name + ".git")
-        if not os.path.isdir(repo):
-            raise NoRepositoryError(app)
-        return repo
-    def makeVersion(self, version):
-        if version not in self.versions:
-            self.versions[version] = ApplicationVersion(distutils.version.LooseVersion(version), self)
-        return self.versions[version]
-    def extract(self, deployment):
-        """Extracts wizard variables from a deployment."""
-        result = {}
-        for k,extractor in self.extractors.items():
-            result[k] = extractor(deployment)
-        return result
-    def parametrize(self, deployment, dir):
-        """Takes a generic source checkout at dir and parametrizes
-        it according to the values of deployment."""
-        variables = deployment.extract()
-        for file in self.parametrized_files:
-            fullpath = os.path.join(dir, file)
-            f = open(fullpath, "r")
-            contents = f.read()
-            f.close()
-            for key, value in variables.items():
-                if value is None: continue
-                contents = contents.replace(key, value)
-            tmp = tempfile.NamedTemporaryFile(delete=False)
-            tmp.write(contents)
-            tmp.close()
-            os.rename(tmp.name, fullpath)
-    @property
-    def extractors(self):
-        return {}
-    @staticmethod
-    def make(name):
-        """Makes an application, but uses the correct subtype if available."""
+class ProductionCopy(Deployment):
+    """
+    Represents the production copy of a deployment.  This copy
+    is canonical, and is the only one guaranteed to be accessible
+    via web, have a database, etc.
+    """
+    @chdir_to_location
+    def upgrade(self, version, options):
+        """
+        Performs an upgrade of database schemas and other non-versioned data.
+        """
+        return self.application.upgrade(self, version, options)
+    @chdir_to_location
+    def backup(self, options):
+        """
+        Performs a backup of database schemas and other non-versioned data.
+        """
+        # There are retarded amounts of race-safety in this function,
+        # because we do NOT want to claim to have made a backup, when
+        # actually something weird happened to it.
+        backupdir = os.path.join(self.scripts_dir, "backups")
+        if not os.path.exists(backupdir):
+            try:
+                os.mkdir(backupdir)
+            except OSError as e:
+                if e.errno == errno.EEXIST:
+                    pass
+                else:
+                    raise
+        tmpdir = tempfile.mkdtemp() # actually will be kept around
         try:
-            __import__("wizard.app." + name)
-            return getattr(wizard.app, name).Application(name)
-        except ImportError:
-            return Application(name)
-
-class ApplicationVersion(object):
-    """Represents an abstract notion of a version for an application"""
-    def __init__(self, version, application):
-        """ `version`       Instance of distutils.LooseVersion
-            `application`   Instance of Application
-        WARNING: Please don't call this directly; instead, use getVersion()
-        on the application you want, so that this version gets registered."""
-        self.version = version
-        self.application = application
-    @property
-    def scripts_tag(self):
-        """Returns the name of the Git tag for this version"""
-        # XXX: This assumes that there's only a -scripts version
-        # which will not be true in the future.  Unfortunately, finding
-        # the "true" latest version is computationally expensive
-        return "v%s-scripts" % self.version
-    def __cmp__(x, y):
-        return cmp(x.version, y.version)
-    @staticmethod
-    def parse(value):
-        """Parses a line from the versions directory and return ApplicationVersion.
-
-        Use this only for cases when speed is of primary importance;
-        the data in version is unreliable and when possible, you should
-        prefer directly instantiating a Deployment and having it query
-        the autoinstall itself for information.
+            self.application.backup(self, tmpdir, options)
+        except app.BackupFailure:
+            # the backup is bogus, don't let it show up
+            shutil.rmtree(tmpdir)
+            raise
+        backup = None
+        with util.LockDirectory(os.path.join(backupdir, "lock")):
+            while 1:
+                backup = str(self.version) + "-" + datetime.datetime.today().strftime("%Y-%m-%dT%H%M%S")
+                outdir = os.path.join(backupdir, backup)
+                if os.path.exists(outdir):
+                    logging.warning("Backup: A backup occurred in the last second. Trying again in a second...")
+                    time.sleep(1)
+                    continue
+                try:
+                    shutil.move(tmpdir, outdir)
+                except:
+                    # don't leave half-baked stuff lying around
+                    try:
+                        shutil.rmtree(outdir)
+                    except OSError:
+                        pass
+                    raise
+                break
+        return backup
+    @chdir_to_location
+    def restore(self, backup, options):
+        """
+        Restores a backup. Destroys state, so be careful! Also, this does
+        NOT restore the file-level backup, which is what 'wizard restore'
+        does, so you probably do NOT want to call this elsewhere unless
+        you know what you're doing (call 'wizard restore' instead).
+        """
+        backup_dir = os.path.join(".scripts", "backups", backup)
+        return self.application.restore(self, backup_dir, options)
+    @chdir_to_location
+    def remove(self, options):
+        """
+        Deletes all non-local or non-filesystem data (such as databases) that
+        this application uses.
+        """
+        self.application.remove(self, options)
+    def verifyWeb(self):
+        """
+        Checks if the autoinstall is viewable from the web.
+        """
+        if not self.application.checkWeb(self):
+            raise WebVerificationError
+    def fetch(self, path, post=None):
+        """
+        Performs a HTTP request on the website.
+        """
+        return util.fetch(self.url.netloc, self.url.path, path, post) # pylint: disable-msg=E1103
 
-        value : The value to parse, will look like:
-           /afs/athena.mit.edu/contrib/scripts/deploy/APP-x.y.z for old style installs
-           APP-x.y.z-scripts for wizard style installs
+class WorkingCopy(Deployment):
+    """
+    Represents a temporary clone of a deployment that we can make
+    modifications to without fear of interfering with a production
+    deployment.  More operations are permitted on these copies.
+    """
+    @chdir_to_location
+    def parametrize(self, deployment):
         """
-        name = value.split("/")[-1]
-        try:
-            if name.find("-") != -1:
-                app, _, version = name.partition("-")
-            else:
-                # kind of poor, maybe should error.  Generally this
-                # will actually result in a not found error
-                app = name
-                version = "trunk"
-        except ValueError:
-            raise DeploymentParseError(deploydir)
-        return ApplicationVersion.make(app, version)
-    @staticmethod
-    def make(app, version):
-        try:
-            # defer to the application for version creation to enforce
-            # singletons
-            return applications()[app].makeVersion(version)
-        except KeyError:
-            raise NoSuchApplication(app)
+        Edits files in ``dir`` to replace WIZARD_* variables with literal
+        instances based on ``deployment``.  This is used for constructing
+        virtual merge bases, and as such ``deployment`` will generally not
+        equal ``self``.
+        """
+        return self.application.parametrize(self, deployment)
+    @chdir_to_location
+    def prepareConfig(self):
+        """
+        Edits files in the deployment such that any user-specific configuration
+        is replaced with generic WIZARD_* variables.
+        """
+        return self.application.prepareConfig(self)
+    @chdir_to_location
+    def resolveConflicts(self):
+        """
+        Resolves conflicted files in this working copy.  Returns whether or
+        not all conflicted files were resolved or not.  Fully resolved
+        files are added to the index, but no commit is made.
+        """
+        return self.application.resolveConflicts(self)
+    @chdir_to_location
+    def prepareMerge(self):
+        """
+        Performs various edits to files in the current working directory in
+        order to make a merge go more smoothly.  This is usually
+        used to fix botched line-endings.
+        """
+        return self.application.prepareMerge(self)
 
 ## -- Exceptions --
 
@@ -252,38 +443,168 @@ class Error(wizard.Error):
     """Base error class for this module"""
     pass
 
-class NoSuchApplication(Error):
-    def __init__(self, app):
-        """app : Application that doesn't exist"""
-        self.app = app
-        self.location = None # filled in when available
-
-class DeploymentParseError(Error):
-    def __init__(self, value):
-        """value : Value from 'versions' that could not be parsed"""
-        self.value = value
-        self.location = None # filled in when available
-
-class NoRepositoryError(Error):
-    def __init__(self, app):
-        """app : The application that doesn't have a Git repository"""
-        self.app = app
-
-# If you want, you can wrap this up into a registry and access things
-# through that, but it's not really necessary
-
-application_list = [
-    "mediawiki", "wordpress", "joomla", "e107", "gallery2",
-    "phpBB", "advancedbook", "phpical", "trac", "turbogears", "django",
-    # these are technically deprecated
-    "advancedpoll", "gallery",
-]
-_applications = None
-
-def applications():
-    """Hash table for looking up string application name to instance"""
-    global _applications
-    if not _applications:
-        _applications = dict([(n,Application.make(n)) for n in application_list ])
-    return _applications
+class NotMigratedError(Error):
+    """
+    The deployment contains a .scripts-version file, but no .git
+    or .scripts directory.
+    """
+    #: Directory of deployment
+    dir = None
+    def __init__(self, dir):
+        self.dir = dir
+    def __str__(self):
+        return """This installation was not migrated"""
+
+class AlreadyVersionedError(Error):
+    """The deployment contained a .git directory but no .scripts directory."""
+    #: Directory of deployment
+    dir = None
+    def __init__(self, dir):
+        self.dir = dir
+    def __str__(self):
+        return """
+
+ERROR: Directory contains a .git directory, but not
+a .scripts directory.  If this is not a corrupt
+migration, this means that the user was versioning their
+install using Git."""
+
+class NotConfiguredError(Error):
+    """The install was missing essential configuration."""
+    #: Directory of unconfigured install
+    dir = None
+    def __init__(self, dir):
+        self.dir = dir
+    def __str__(self):
+        return """
+
+ERROR: The install was well-formed, but not configured
+(essential configuration files were not found.)"""
+
+class CorruptedAutoinstallError(Error):
+    """The install was missing a .git directory, but had a .scripts directory."""
+    #: Directory of the corrupted install
+    dir = None
+    def __init__(self, dir):
+        self.dir = dir
+    def __str__(self):
+        return """
+
+ERROR: Directory contains a .scripts directory,
+but not a .git directory."""
+
+class NotAutoinstallError(Error):
+    """The directory was not an autoinstall, due to missing .scripts-version file."""
+    #: Directory in question
+    dir = None
+    def __init__(self, dir):
+        self.dir = dir
+    def __str__(self):
+        return """
+
+ERROR: Could not find .scripts-version file. Are you sure
+this is an autoinstalled application?
+"""
+
+class NoTagError(Error):
+    """Deployment has a tag that does not have an equivalent in upstream repository."""
+    #: Missing tag
+    tag = None
+    def __init__(self, tag):
+        self.tag = tag
+    def __str__(self):
+        return """
+
+ERROR: Could not find tag %s in repository.""" % self.tag
+
+class NoLocalTagError(Error):
+    """Could not find tag in local repository."""
+    #: Missing tag
+    tag = None
+    def __init__(self, tag):
+        self.tag = tag
+    def __str__(self):
+        return """
+
+ERROR: Could not find tag %s in local repository.""" % self.tag
+
+class InconsistentPristineTagError(Error):
+    """Pristine tag commit ID does not match upstream pristine tag commit ID."""
+    #: Inconsistent tag
+    tag = None
+    def __init__(self, tag):
+        self.tag = tag
+    def __str__(self):
+        return """
+
+ERROR: Local pristine tag %s did not match repository's.  This
+probably means an upstream rebase occured.""" % self.tag
+
+class InconsistentScriptsTagError(Error):
+    """Scripts tag commit ID does not match upstream scripts tag commit ID."""
+    #: Inconsistent tag
+    tag = None
+    def __init__(self, tag):
+        self.tag = tag
+    def __str__(self):
+        return """
+
+ERROR: Local scripts tag %s did not match repository's.  This
+probably means an upstream rebase occurred.""" % self.tag
+
+class HeadNotDescendantError(Error):
+    """HEAD is not connected to tag."""
+    #: Tag that HEAD should have been descendant of.
+    tag = None
+    def __init__(self, tag):
+        self.tag = tag
+    def __str__(self):
+        return """
+
+ERROR: HEAD is not a descendant of %s.  This probably
+means that an upstream rebase occurred, and new tags were
+pulled, but local user commits were never rebased.""" % self.tag
+
+class VersionDetectionError(Error):
+    """Could not detect real version of application."""
+    def __str__(self):
+        return """
+
+ERROR: Could not detect the real version of the application."""
+
+class VersionMismatchError(Error):
+    """Git version of application does not match detected version."""
+    #: Detected version
+    real_version = None
+    #: Version from Git
+    git_version = None
+    def __init__(self, real_version, git_version):
+        self.real_version = real_version
+        self.git_version = git_version
+    def __str__(self):
+        return """
+
+ERROR: The detected version %s did not match the Git
+version %s.""" % (self.real_version, self.git_version)
+
+class WebVerificationError(Error):
+    """Could not access the application on the web"""
+    def __str__(self):
+        return """
+
+ERROR: We were not able to access the application on the
+web.  This may indicate that the website is behind
+authentication on the htaccess level.  You can find
+the contents of the page from the debug backtraces."""
+
+class UnknownWebPath(Error):
+    """Could not determine application's web path."""
+    def __str__(self):
+        return """
+
+ERROR: We were not able to determine what the application's
+host and path were in order to perform a web request
+on the application.  You can specify this manually using
+the WIZARD_WEB_HOST and WIZARD_WEB_PATH environment
+variables."""