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filemerge: add support for partial conflict resolution by external tool...
filemerge: add support for partial conflict resolution by external tool A common class of merge conflicts is in imports/#includes/etc. It's relatively easy to write a tool that can resolve these conflicts, perhaps by naively just unioning the statements and leaving any cleanup to other tools to do later [1]. Such specialized tools cannot generally resolve all conflicts in a file, of course. Let's therefore call them "partial merge tools". Note that the internal simplemerge algorithm is such a partial merge tool - one that only resolves trivial "conflicts" where one side is unchanged or both sides change in the same way. One can also imagine having smarter language-aware partial tools that merge the AST. It may be useful for such tools to interactively let the user resolve any conflicts it can't resolve itself. However, having the option of implementing it as a partial merge tool means that the developer doesn't *need* to create a UI for it. Instead, the user can resolve any remaining conflicts with their regular merge tool (e.g. `:merge3` or `meld). We don't currently have a way to let the user define such partial merge tools. That's what this patch addresses. It lets the user configure partial merge tools to run. Each tool can be configured to run only on files matching certain patterns (e.g. "*.py"). The tool takes three inputs (local, base, other) and resolves conflicts by updating these in place. For example, let's say the inputs are these: base: ``` import sys def main(): print('Hello') ``` local: ``` import os import sys def main(): print('Hi') ``` other: ``` import re import sys def main(): print('Howdy') ``` A partial merge tool could now resolve the conflicting imports by replacing the import statements in *all* files by the following snippet, while leaving the remainder of the files unchanged. ``` import os import re import sys ``` As a result, simplemerge and any regular merge tool that runs after the partial merge tool(s) will consider the imports to be non-conflicting and will only present the conflict in `main()` to the user. Differential Revision: https://phab.mercurial-scm.org/D12356

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simplemerge
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#!/usr/bin/env python3
import getopt
import sys
import hgdemandimport
hgdemandimport.enable()
from mercurial.i18n import _
from mercurial import (
context,
error,
fancyopts,
simplemerge,
ui as uimod,
util,
)
from mercurial.utils import procutil, stringutil
options = [
(b'L', b'label', [], _(b'labels to use on conflict markers')),
(b'a', b'text', None, _(b'treat all files as text')),
(b'p', b'print', None, _(b'print results instead of overwriting LOCAL')),
(b'', b'no-minimal', None, _(b'no effect (DEPRECATED)')),
(b'h', b'help', None, _(b'display help and exit')),
(b'q', b'quiet', None, _(b'suppress output')),
]
usage = _(
b'''simplemerge [OPTS] LOCAL BASE OTHER
Simple three-way file merge utility with a minimal feature set.
Apply to LOCAL the changes necessary to go from BASE to OTHER.
By default, LOCAL is overwritten with the results of this operation.
'''
)
class ParseError(Exception):
"""Exception raised on errors in parsing the command line."""
def showhelp():
procutil.stdout.write(usage)
procutil.stdout.write(b'\noptions:\n')
out_opts = []
for shortopt, longopt, default, desc in options:
out_opts.append(
(
b'%2s%s'
% (
shortopt and b'-%s' % shortopt,
longopt and b' --%s' % longopt,
),
b'%s' % desc,
)
)
opts_len = max([len(opt[0]) for opt in out_opts])
for first, second in out_opts:
procutil.stdout.write(b' %-*s %s\n' % (opts_len, first, second))
def _verifytext(input, ui, quiet=False, allow_binary=False):
"""verifies that text is non-binary (unless opts[text] is passed,
then we just warn)"""
if stringutil.binary(input.text()):
msg = _(b"%s looks like a binary file.") % input.fctx.path()
if not quiet:
ui.warn(_(b'warning: %s\n') % msg)
if not allow_binary:
sys.exit(1)
try:
for fp in (sys.stdin, procutil.stdout, sys.stderr):
procutil.setbinary(fp)
opts = {}
try:
bargv = [a.encode('utf8') for a in sys.argv[1:]]
args = fancyopts.fancyopts(bargv, options, opts)
except getopt.GetoptError as e:
raise ParseError(e)
if opts[b'help']:
showhelp()
sys.exit(0)
if len(args) != 3:
raise ParseError(_(b'wrong number of arguments').decode('utf8'))
mode = b'merge'
if len(opts[b'label']) > 2:
mode = b'merge3'
local, base, other = args
overrides = opts[b'label']
if len(overrides) > 3:
raise error.InputError(b'can only specify three labels.')
labels = [local, other, base]
labels[: len(overrides)] = overrides
local_input = simplemerge.MergeInput(
context.arbitraryfilectx(local), labels[0]
)
other_input = simplemerge.MergeInput(
context.arbitraryfilectx(other), labels[1]
)
base_input = simplemerge.MergeInput(
context.arbitraryfilectx(base), labels[2]
)
quiet = opts.get(b'quiet')
allow_binary = opts.get(b'text')
ui = uimod.ui.load()
_verifytext(local_input, ui, quiet=quiet, allow_binary=allow_binary)
_verifytext(base_input, ui, quiet=quiet, allow_binary=allow_binary)
_verifytext(other_input, ui, quiet=quiet, allow_binary=allow_binary)
merged_text, conflicts = simplemerge.simplemerge(
local_input,
base_input,
other_input,
mode,
allow_binary=allow_binary,
)
if opts.get(b'print'):
ui.fout.write(merged_text)
else:
util.writefile(local, merged_text)
sys.exit(1 if conflicts else 0)
except ParseError as e:
e = stringutil.forcebytestr(e)
procutil.stdout.write(b"%s: %s\n" % (sys.argv[0].encode('utf8'), e))
showhelp()
sys.exit(1)
except error.Abort as e:
procutil.stderr.write(b"abort: %s\n" % e)
sys.exit(255)
except KeyboardInterrupt:
sys.exit(255)