4 This module contains algorithms for performing conflict
5 resolution after Git performs its recursive merge. It
6 defines a simple domain specific language (that, at
7 its simplest form, merely involves copying conflict markers
8 and writing in the form that they should be resolved as) for
9 specifying how to resolve conflicts. These are mostly relevant
10 for resolving conflicts in configuration files.
12 The conflict resolution DSL is described here:
14 Resolutions are specified as input-output pairs. An input
15 is a string with the conflict resolution markers ("<" * 7,
16 "=" * 7 and ">" * 7), with the HEAD content above the equals
17 divider, and the upstream content below the equals divider.
18 Lines can also be marked as "***N***" where N is a natural
19 number greater than 0 (i.e. 1 or more), which means that
20 an arbitrary number of lines may be matched and available for output.
22 Output is a list of integers and strings. Integers expand
23 to lines that were specified earlier; -1 and 0 are special integers
24 that correspond to the entire HEAD text, and the entire upstream
25 text, respectively. Strings can be used to insert custom lines.
27 The DSL does not currently claim to support character level granularity.
28 It also does not claim to support contiguous conflicts.
29 Our hope is that this simple syntax will be sufficient to cover
30 most common merge failures.
32 Here are some examples::
40 With ``[-1]`` would discard all upstream changes, whereas with ``[0]``
41 would discard downstream changes (you would probably want to be
42 careful about wildcarding in the upstream string).
44 Pattern matching in action::
56 With ``[0, 1, 2, 3]`` would resolve with the new upstream text, and
57 then the user matched globs.
63 re_var = re.compile("^\*\*\*(\d+)\*\*\*\\\n", re.MULTILINE)
65 def spec_to_regex(spec):
67 Translates a specification string into a regular expression tuple.
68 Note that pattern matches are out of order, so the second element
69 of the tuple is a dict specified strings to subpattern numbers.
70 Requires re.DOTALL for correct operation.
72 ours, _, theirs = "".join(spec.strip().splitlines(True)[1:-1]).partition("=======\n")
73 def regexify(text, fullmatch, matchno):
74 text_split = re.split(re_var, text)
76 mappings = {fullmatch: matchno}
77 for is_var, line in zip(itertools.cycle([False, True]), text_split):
81 mappings[int(line)] = matchno
83 ret += re.escape(line)
84 return ("(" + ret + ")", mappings)
85 ours_regex, ours_mappings = regexify(ours, -1, 1)
86 theirs_regex, theirs_mappings = regexify(theirs, 0, len(ours_mappings) + 1)
87 ours_mappings.update(theirs_mappings)
88 return ("<<<<<<<[^\n]*\\\n" + ours_regex + "=======\\\n" + theirs_regex + ">>>>>>>[^\n]*(\\\n|$)", ours_mappings)
90 def result_to_repl(result, mappings):
91 def ritem_to_string(r):
93 return "\\%d" % mappings[r]
96 return "".join(map(ritem_to_string, result))
98 def resolve(contents, spec, result):
99 rstring, mappings = spec_to_regex(spec)
100 regex = re.compile(rstring, re.DOTALL)
101 repl = result_to_repl(result, mappings)
105 for line in contents.splitlines(True):
106 if status == 0 and line.startswith("<<<<<<<"):
108 elif status == 1 and line.startswith("======="):
111 if status == 2 and line.startswith(">>>>>>>"):
114 ret += regex.sub(repl, conflict)
122 def is_conflict(contents):
123 # Really really simple heuristic
124 return "<<<<<<<" in contents