simplemerge: take arguments as annotated context objects

The labels we put in conflict markers are formatted so the part before
the ':' (typically says things like "local") is padded so the ':' is
aligned among the labels. That means that if you specify a long label
for "base" but the conflict marker style is "merge" (i.e. 2-way), the
other two will have unwanted padding. We often don't specify a label
for the base, so we don't notice the problem (and it may very well be
that it didn't exist before my D11972).

I think the best fix is to pass the labels along with the context
objects, so the low-level code that switches on the marker style to
use (i.e. `simplemerge`) can do the formatting. This patch starts
doing that by passing a fully-formatted label to `simplemerge`. A
coming patch will move the formatting to `simplemerge`.

Differential Revision: https://phab.mercurial-scm.org/D12013

contrib/simplemerge

@@ -1,108 +1,118 b''
 #!/usr/bin/env python3
 from __future__ import absolute_import
 
 import getopt
 import sys
 
 import hgdemandimport
 
 hgdemandimport.enable()
 
 from mercurial.i18n import _
 from mercurial import (
     context,
     error,
     fancyopts,
     pycompat,
     simplemerge,
     ui as uimod,
 )
 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))
 
 
 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'))
     if len(opts[b'label']) > 2:
         opts[b'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
-    opts[b'label'] = labels
+    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]
+    )
     sys.exit(
         simplemerge.simplemerge(
             uimod.ui.load(),
-            context.arbitraryfilectx(local),
-            context.arbitraryfilectx(base),
-            context.arbitraryfilectx(other),
+            local_input,
+            base_input,
+            other_input,
             **pycompat.strkwargs(opts)
         )
     )
 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)

mercurial/filemerge.py

@@ -1,1278 +1,1290 b''
 # filemerge.py - file-level merge handling for Mercurial
 #
 # Copyright 2006, 2007, 2008 Olivia Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import contextlib
 import os
 import re
 import shutil
 
 from .i18n import _
 from .node import (
     hex,
     short,
 )
 from .pycompat import (
     getattr,
     open,
 )
 
 from . import (
     encoding,
     error,
     formatter,
     match,
     pycompat,
     registrar,
     scmutil,
     simplemerge,
     tagmerge,
     templatekw,
     templater,
     templateutil,
     util,
 )
 
 from .utils import (
     procutil,
     stringutil,
 )
 
 
 def _toolstr(ui, tool, part, *args):
     return ui.config(b"merge-tools", tool + b"." + part, *args)
 
 
 def _toolbool(ui, tool, part, *args):
     return ui.configbool(b"merge-tools", tool + b"." + part, *args)
 
 
 def _toollist(ui, tool, part):
     return ui.configlist(b"merge-tools", tool + b"." + part)
 
 
 internals = {}
 # Merge tools to document.
 internalsdoc = {}
 
 internaltool = registrar.internalmerge()
 
 # internal tool merge types
 nomerge = internaltool.nomerge
 mergeonly = internaltool.mergeonly  # just the full merge, no premerge
 fullmerge = internaltool.fullmerge  # both premerge and merge
 
 # IMPORTANT: keep the last line of this prompt very short ("What do you want to
 # do?") because of issue6158, ideally to <40 English characters (to allow other
 # languages that may take more columns to still have a chance to fit in an
 # 80-column screen).
 _localchangedotherdeletedmsg = _(
     b"file '%(fd)s' was deleted in other%(o)s but was modified in local%(l)s.\n"
     b"You can use (c)hanged version, (d)elete, or leave (u)nresolved.\n"
     b"What do you want to do?"
     b"$$ &Changed $$ &Delete $$ &Unresolved"
 )
 
 _otherchangedlocaldeletedmsg = _(
     b"file '%(fd)s' was deleted in local%(l)s but was modified in other%(o)s.\n"
     b"You can use (c)hanged version, leave (d)eleted, or leave (u)nresolved.\n"
     b"What do you want to do?"
     b"$$ &Changed $$ &Deleted $$ &Unresolved"
 )
 
 
 class absentfilectx(object):
     """Represents a file that's ostensibly in a context but is actually not
     present in it.
 
     This is here because it's very specific to the filemerge code for now --
     other code is likely going to break with the values this returns."""
 
     def __init__(self, ctx, f):
         self._ctx = ctx
         self._f = f
 
     def __bytes__(self):
         return b'absent file %s@%s' % (self._f, self._ctx)
 
     def path(self):
         return self._f
 
     def size(self):
         return None
 
     def data(self):
         return None
 
     def filenode(self):
         return self._ctx.repo().nullid
 
     _customcmp = True
 
     def cmp(self, fctx):
         """compare with other file context
 
         returns True if different from fctx.
         """
         return not (
             fctx.isabsent()
             and fctx.changectx() == self.changectx()
             and fctx.path() == self.path()
         )
 
     def flags(self):
         return b''
 
     def changectx(self):
         return self._ctx
 
     def isbinary(self):
         return False
 
     def isabsent(self):
         return True
 
 
 def _findtool(ui, tool):
     if tool in internals:
         return tool
     cmd = _toolstr(ui, tool, b"executable", tool)
     if cmd.startswith(b'python:'):
         return cmd
     return findexternaltool(ui, tool)
 
 
 def _quotetoolpath(cmd):
     if cmd.startswith(b'python:'):
         return cmd
     return procutil.shellquote(cmd)
 
 
 def findexternaltool(ui, tool):
     for kn in (b"regkey", b"regkeyalt"):
         k = _toolstr(ui, tool, kn)
         if not k:
             continue
         p = util.lookupreg(k, _toolstr(ui, tool, b"regname"))
         if p:
             p = procutil.findexe(p + _toolstr(ui, tool, b"regappend", b""))
             if p:
                 return p
     exe = _toolstr(ui, tool, b"executable", tool)
     return procutil.findexe(util.expandpath(exe))
 
 
 def _picktool(repo, ui, path, binary, symlink, changedelete):
     strictcheck = ui.configbool(b'merge', b'strict-capability-check')
 
     def hascapability(tool, capability, strict=False):
         if tool in internals:
             return strict and internals[tool].capabilities.get(capability)
         return _toolbool(ui, tool, capability)
 
     def supportscd(tool):
         return tool in internals and internals[tool].mergetype == nomerge
 
     def check(tool, pat, symlink, binary, changedelete):
         tmsg = tool
         if pat:
             tmsg = _(b"%s (for pattern %s)") % (tool, pat)
         if not _findtool(ui, tool):
             if pat:  # explicitly requested tool deserves a warning
                 ui.warn(_(b"couldn't find merge tool %s\n") % tmsg)
             else:  # configured but non-existing tools are more silent
                 ui.note(_(b"couldn't find merge tool %s\n") % tmsg)
         elif symlink and not hascapability(tool, b"symlink", strictcheck):
             ui.warn(_(b"tool %s can't handle symlinks\n") % tmsg)
         elif binary and not hascapability(tool, b"binary", strictcheck):
             ui.warn(_(b"tool %s can't handle binary\n") % tmsg)
         elif changedelete and not supportscd(tool):
             # the nomerge tools are the only tools that support change/delete
             # conflicts
             pass
         elif not procutil.gui() and _toolbool(ui, tool, b"gui"):
             ui.warn(_(b"tool %s requires a GUI\n") % tmsg)
         else:
             return True
         return False
 
     # internal config: ui.forcemerge
     # forcemerge comes from command line arguments, highest priority
     force = ui.config(b'ui', b'forcemerge')
     if force:
         toolpath = _findtool(ui, force)
         if changedelete and not supportscd(toolpath):
             return b":prompt", None
         else:
             if toolpath:
                 return (force, _quotetoolpath(toolpath))
             else:
                 # mimic HGMERGE if given tool not found
                 return (force, force)
 
     # HGMERGE takes next precedence
     hgmerge = encoding.environ.get(b"HGMERGE")
     if hgmerge:
         if changedelete and not supportscd(hgmerge):
             return b":prompt", None
         else:
             return (hgmerge, hgmerge)
 
     # then patterns
 
     # whether binary capability should be checked strictly
     binarycap = binary and strictcheck
 
     for pat, tool in ui.configitems(b"merge-patterns"):
         mf = match.match(repo.root, b'', [pat])
         if mf(path) and check(tool, pat, symlink, binarycap, changedelete):
             if binary and not hascapability(tool, b"binary", strict=True):
                 ui.warn(
                     _(
                         b"warning: check merge-patterns configurations,"
                         b" if %r for binary file %r is unintentional\n"
                         b"(see 'hg help merge-tools'"
                         b" for binary files capability)\n"
                     )
                     % (pycompat.bytestr(tool), pycompat.bytestr(path))
                 )
             toolpath = _findtool(ui, tool)
             return (tool, _quotetoolpath(toolpath))
 
     # then merge tools
     tools = {}
     disabled = set()
     for k, v in ui.configitems(b"merge-tools"):
         t = k.split(b'.')[0]
         if t not in tools:
             tools[t] = int(_toolstr(ui, t, b"priority"))
         if _toolbool(ui, t, b"disabled"):
             disabled.add(t)
     names = tools.keys()
     tools = sorted(
         [(-p, tool) for tool, p in tools.items() if tool not in disabled]
     )
     uimerge = ui.config(b"ui", b"merge")
     if uimerge:
         # external tools defined in uimerge won't be able to handle
         # change/delete conflicts
         if check(uimerge, path, symlink, binary, changedelete):
             if uimerge not in names and not changedelete:
                 return (uimerge, uimerge)
             tools.insert(0, (None, uimerge))  # highest priority
     tools.append((None, b"hgmerge"))  # the old default, if found
     for p, t in tools:
         if check(t, None, symlink, binary, changedelete):
             toolpath = _findtool(ui, t)
             return (t, _quotetoolpath(toolpath))
 
     # internal merge or prompt as last resort
     if symlink or binary or changedelete:
         if not changedelete and len(tools):
             # any tool is rejected by capability for symlink or binary
             ui.warn(_(b"no tool found to merge %s\n") % path)
         return b":prompt", None
     return b":merge", None
 
 
 def _eoltype(data):
     """Guess the EOL type of a file"""
     if b'\0' in data:  # binary
         return None
     if b'\r\n' in data:  # Windows
         return b'\r\n'
     if b'\r' in data:  # Old Mac
         return b'\r'
     if b'\n' in data:  # UNIX
         return b'\n'
     return None  # unknown
 
 
 def _matcheol(file, backup):
     """Convert EOL markers in a file to match origfile"""
     tostyle = _eoltype(backup.data())  # No repo.wread filters?
     if tostyle:
         data = util.readfile(file)
         style = _eoltype(data)
         if style:
             newdata = data.replace(style, tostyle)
             if newdata != data:
                 util.writefile(file, newdata)
 
 
 @internaltool(b'prompt', nomerge)
 def _iprompt(repo, mynode, fcd, fco, fca, toolconf, labels=None):
     """Asks the user which of the local `p1()` or the other `p2()` version to
     keep as the merged version."""
     ui = repo.ui
     fd = fcd.path()
     uipathfn = scmutil.getuipathfn(repo)
 
     # Avoid prompting during an in-memory merge since it doesn't support merge
     # conflicts.
     if fcd.changectx().isinmemory():
         raise error.InMemoryMergeConflictsError(
             b'in-memory merge does not support file conflicts'
         )
 
     prompts = partextras(labels)
     prompts[b'fd'] = uipathfn(fd)
     try:
         if fco.isabsent():
             index = ui.promptchoice(_localchangedotherdeletedmsg % prompts, 2)
             choice = [b'local', b'other', b'unresolved'][index]
         elif fcd.isabsent():
             index = ui.promptchoice(_otherchangedlocaldeletedmsg % prompts, 2)
             choice = [b'other', b'local', b'unresolved'][index]
         else:
             # IMPORTANT: keep the last line of this prompt ("What do you want to
             # do?") very short, see comment next to _localchangedotherdeletedmsg
             # at the top of the file for details.
             index = ui.promptchoice(
                 _(
                     b"file '%(fd)s' needs to be resolved.\n"
                     b"You can keep (l)ocal%(l)s, take (o)ther%(o)s, or leave "
                     b"(u)nresolved.\n"
                     b"What do you want to do?"
                     b"$$ &Local $$ &Other $$ &Unresolved"
                 )
                 % prompts,
                 2,
             )
             choice = [b'local', b'other', b'unresolved'][index]
 
         if choice == b'other':
             return _iother(repo, mynode, fcd, fco, fca, toolconf, labels)
         elif choice == b'local':
             return _ilocal(repo, mynode, fcd, fco, fca, toolconf, labels)
         elif choice == b'unresolved':
             return _ifail(repo, mynode, fcd, fco, fca, toolconf, labels)
     except error.ResponseExpected:
         ui.write(b"\n")
         return _ifail(repo, mynode, fcd, fco, fca, toolconf, labels)
 
 
 @internaltool(b'local', nomerge)
 def _ilocal(repo, mynode, fcd, fco, fca, toolconf, labels=None):
     """Uses the local `p1()` version of files as the merged version."""
     return 0, fcd.isabsent()
 
 
 @internaltool(b'other', nomerge)
 def _iother(repo, mynode, fcd, fco, fca, toolconf, labels=None):
     """Uses the other `p2()` version of files as the merged version."""
     if fco.isabsent():
         # local changed, remote deleted -- 'deleted' picked
         _underlyingfctxifabsent(fcd).remove()
         deleted = True
     else:
         _underlyingfctxifabsent(fcd).write(fco.data(), fco.flags())
         deleted = False
     return 0, deleted
 
 
 @internaltool(b'fail', nomerge)
 def _ifail(repo, mynode, fcd, fco, fca, toolconf, labels=None):
     """
     Rather than attempting to merge files that were modified on both
     branches, it marks them as unresolved. The resolve command must be
     used to resolve these conflicts."""
     # for change/delete conflicts write out the changed version, then fail
     if fcd.isabsent():
         _underlyingfctxifabsent(fcd).write(fco.data(), fco.flags())
     return 1, False
 
 
 def _underlyingfctxifabsent(filectx):
     """Sometimes when resolving, our fcd is actually an absentfilectx, but
     we want to write to it (to do the resolve). This helper returns the
     underyling workingfilectx in that case.
     """
     if filectx.isabsent():
         return filectx.changectx()[filectx.path()]
     else:
         return filectx
 
 
 def _premerge(repo, fcd, fco, fca, toolconf, backup, labels):
     tool, toolpath, binary, symlink, scriptfn = toolconf
     if symlink or fcd.isabsent() or fco.isabsent():
         return 1
 
     ui = repo.ui
 
     validkeep = [b'keep', b'keep-merge3', b'keep-mergediff']
 
     # do we attempt to simplemerge first?
     try:
         premerge = _toolbool(ui, tool, b"premerge", not binary)
     except error.ConfigError:
         premerge = _toolstr(ui, tool, b"premerge", b"").lower()
         if premerge not in validkeep:
             _valid = b', '.join([b"'" + v + b"'" for v in validkeep])
             raise error.ConfigError(
                 _(b"%s.premerge not valid ('%s' is neither boolean nor %s)")
                 % (tool, premerge, _valid)
             )
 
     if premerge:
         if len(labels) < 3:
             labels.append(b'base')
         mode = b'merge'
         if premerge == b'keep-mergediff':
             mode = b'mergediff'
         elif premerge == b'keep-merge3':
             mode = b'merge3'
+        local = simplemerge.MergeInput(fcd, labels[0])
+        other = simplemerge.MergeInput(fco, labels[1])
+        base = simplemerge.MergeInput(fca, labels[2])
         r = simplemerge.simplemerge(
-            ui, fcd, fca, fco, quiet=True, label=labels, mode=mode
+            ui, local, base, other, quiet=True, mode=mode
         )
         if not r:
             ui.debug(b" premerge successful\n")
             return 0
         if premerge not in validkeep:
             # restore from backup and try again
             _restorebackup(fcd, backup)
     return 1  # continue merging
 
 
 def _mergecheck(repo, mynode, fcd, fco, fca, toolconf):
     tool, toolpath, binary, symlink, scriptfn = toolconf
     uipathfn = scmutil.getuipathfn(repo)
     if symlink:
         repo.ui.warn(
             _(b'warning: internal %s cannot merge symlinks for %s\n')
             % (tool, uipathfn(fcd.path()))
         )
         return False
     if fcd.isabsent() or fco.isabsent():
         repo.ui.warn(
             _(
                 b'warning: internal %s cannot merge change/delete '
                 b'conflict for %s\n'
             )
             % (tool, uipathfn(fcd.path()))
         )
         return False
     return True
 
 
 def _merge(repo, mynode, fcd, fco, fca, toolconf, backup, labels, mode):
     """
     Uses the internal non-interactive simple merge algorithm for merging
     files. It will fail if there are any conflicts and leave markers in
     the partially merged file. Markers will have two sections, one for each side
     of merge, unless mode equals 'union' which suppresses the markers."""
     ui = repo.ui
 
-    r = simplemerge.simplemerge(ui, fcd, fca, fco, label=labels, mode=mode)
+    local = simplemerge.MergeInput(fcd)
+    if len(labels) > 0:
+        local.label = labels[0]
+    other = simplemerge.MergeInput(fco)
+    if len(labels) > 1:
+        other.label = labels[1]
+    base = simplemerge.MergeInput(fca)
+    if len(labels) > 2:
+        base.label = labels[2]
+    r = simplemerge.simplemerge(ui, local, base, other, mode=mode)
     return True, r, False
 
 
 @internaltool(
     b'union',
     fullmerge,
     _(
         b"warning: conflicts while merging %s! "
         b"(edit, then use 'hg resolve --mark')\n"
     ),
     precheck=_mergecheck,
 )
 def _iunion(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Uses the internal non-interactive simple merge algorithm for merging
     files. It will use both left and right sides for conflict regions.
     No markers are inserted."""
     return _merge(
         repo, mynode, fcd, fco, fca, toolconf, backup, labels, b'union'
     )
 
 
 @internaltool(
     b'merge',
     fullmerge,
     _(
         b"warning: conflicts while merging %s! "
         b"(edit, then use 'hg resolve --mark')\n"
     ),
     precheck=_mergecheck,
 )
 def _imerge(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Uses the internal non-interactive simple merge algorithm for merging
     files. It will fail if there are any conflicts and leave markers in
     the partially merged file. Markers will have two sections, one for each side
     of merge."""
     return _merge(
         repo, mynode, fcd, fco, fca, toolconf, backup, labels, b'merge'
     )
 
 
 @internaltool(
     b'merge3',
     fullmerge,
     _(
         b"warning: conflicts while merging %s! "
         b"(edit, then use 'hg resolve --mark')\n"
     ),
     precheck=_mergecheck,
 )
 def _imerge3(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Uses the internal non-interactive simple merge algorithm for merging
     files. It will fail if there are any conflicts and leave markers in
     the partially merged file. Marker will have three sections, one from each
     side of the merge and one for the base content."""
     if not labels:
         labels = _defaultconflictlabels
     if len(labels) < 3:
         labels.append(b'base')
     return _merge(
         repo, mynode, fcd, fco, fca, toolconf, backup, labels, b'merge3'
     )
 
 
 @internaltool(
     b'merge3-lie-about-conflicts',
     fullmerge,
     b'',
     precheck=_mergecheck,
 )
 def _imerge3alwaysgood(*args, **kwargs):
     # Like merge3, but record conflicts as resolved with markers in place.
     #
     # This is used for `diff.merge` to show the differences between
     # the auto-merge state and the committed merge state. It may be
     # useful for other things.
     b1, junk, b2 = _imerge3(*args, **kwargs)
     # TODO is this right? I'm not sure what these return values mean,
     # but as far as I can tell this will indicate to callers tha the
     # merge succeeded.
     return b1, False, b2
 
 
 @internaltool(
     b'mergediff',
     fullmerge,
     _(
         b"warning: conflicts while merging %s! "
         b"(edit, then use 'hg resolve --mark')\n"
     ),
     precheck=_mergecheck,
 )
 def _imerge_diff(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Uses the internal non-interactive simple merge algorithm for merging
     files. It will fail if there are any conflicts and leave markers in
     the partially merged file. The marker will have two sections, one with the
     content from one side of the merge, and one with a diff from the base
     content to the content on the other side. (experimental)"""
     if not labels:
         labels = _defaultconflictlabels
     if len(labels) < 3:
         labels.append(b'base')
     return _merge(
         repo, mynode, fcd, fco, fca, toolconf, backup, labels, b'mergediff'
     )
 
 
 @internaltool(b'merge-local', mergeonly, precheck=_mergecheck)
 def _imergelocal(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Like :merge, but resolve all conflicts non-interactively in favor
     of the local `p1()` changes."""
     return _merge(
         repo, mynode, fcd, fco, fca, toolconf, backup, labels, b'local'
     )
 
 
 @internaltool(b'merge-other', mergeonly, precheck=_mergecheck)
 def _imergeother(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Like :merge, but resolve all conflicts non-interactively in favor
     of the other `p2()` changes."""
     return _merge(
         repo, mynode, fcd, fco, fca, toolconf, backup, labels, b'other'
     )
 
 
 @internaltool(
     b'tagmerge',
     mergeonly,
     _(
         b"automatic tag merging of %s failed! "
         b"(use 'hg resolve --tool :merge' or another merge "
         b"tool of your choice)\n"
     ),
 )
 def _itagmerge(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Uses the internal tag merge algorithm (experimental).
     """
     success, status = tagmerge.merge(repo, fcd, fco, fca)
     return success, status, False
 
 
 @internaltool(b'dump', fullmerge, binary=True, symlink=True)
 def _idump(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Creates three versions of the files to merge, containing the
     contents of local, other and base. These files can then be used to
     perform a merge manually. If the file to be merged is named
     ``a.txt``, these files will accordingly be named ``a.txt.local``,
     ``a.txt.other`` and ``a.txt.base`` and they will be placed in the
     same directory as ``a.txt``.
 
     This implies premerge. Therefore, files aren't dumped, if premerge
     runs successfully. Use :forcedump to forcibly write files out.
     """
     a = _workingpath(repo, fcd)
     fd = fcd.path()
 
     from . import context
 
     if isinstance(fcd, context.overlayworkingfilectx):
         raise error.InMemoryMergeConflictsError(
             b'in-memory merge does not support the :dump tool.'
         )
 
     util.writefile(a + b".local", fcd.decodeddata())
     repo.wwrite(fd + b".other", fco.data(), fco.flags())
     repo.wwrite(fd + b".base", fca.data(), fca.flags())
     return False, 1, False
 
 
 @internaltool(b'forcedump', mergeonly, binary=True, symlink=True)
 def _forcedump(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     """
     Creates three versions of the files as same as :dump, but omits premerge.
     """
     return _idump(repo, mynode, fcd, fco, fca, toolconf, backup, labels=labels)
 
 
 def _xmergeimm(repo, mynode, fcd, fco, fca, toolconf, backup, labels=None):
     # In-memory merge simply raises an exception on all external merge tools,
     # for now.
     #
     # It would be possible to run most tools with temporary files, but this
     # raises the question of what to do if the user only partially resolves the
     # file -- we can't leave a merge state. (Copy to somewhere in the .hg/
     # directory and tell the user how to get it is my best idea, but it's
     # clunky.)
     raise error.InMemoryMergeConflictsError(
         b'in-memory merge does not support external merge tools'
     )
 
 
 def _describemerge(ui, repo, mynode, fcl, fcb, fco, env, toolpath, args):
     tmpl = ui.config(b'command-templates', b'pre-merge-tool-output')
     if not tmpl:
         return
 
     mappingdict = templateutil.mappingdict
     props = {
         b'ctx': fcl.changectx(),
         b'node': hex(mynode),
         b'path': fcl.path(),
         b'local': mappingdict(
             {
                 b'ctx': fcl.changectx(),
                 b'fctx': fcl,
                 b'node': hex(mynode),
                 b'name': _(b'local'),
                 b'islink': b'l' in fcl.flags(),
                 b'label': env[b'HG_MY_LABEL'],
             }
         ),
         b'base': mappingdict(
             {
                 b'ctx': fcb.changectx(),
                 b'fctx': fcb,
                 b'name': _(b'base'),
                 b'islink': b'l' in fcb.flags(),
                 b'label': env[b'HG_BASE_LABEL'],
             }
         ),
         b'other': mappingdict(
             {
                 b'ctx': fco.changectx(),
                 b'fctx': fco,
                 b'name': _(b'other'),
                 b'islink': b'l' in fco.flags(),
                 b'label': env[b'HG_OTHER_LABEL'],
             }
         ),
         b'toolpath': toolpath,
         b'toolargs': args,
     }
 
     # TODO: make all of this something that can be specified on a per-tool basis
     tmpl = templater.unquotestring(tmpl)
 
     # Not using cmdutil.rendertemplate here since it causes errors importing
     # things for us to import cmdutil.
     tres = formatter.templateresources(ui, repo)
     t = formatter.maketemplater(
         ui, tmpl, defaults=templatekw.keywords, resources=tres
     )
     ui.status(t.renderdefault(props))
 
 
 def _xmerge(repo, mynode, fcd, fco, fca, toolconf, backup, labels):
     tool, toolpath, binary, symlink, scriptfn = toolconf
     uipathfn = scmutil.getuipathfn(repo)
     if fcd.isabsent() or fco.isabsent():
         repo.ui.warn(
             _(b'warning: %s cannot merge change/delete conflict for %s\n')
             % (tool, uipathfn(fcd.path()))
         )
         return False, 1, None
     localpath = _workingpath(repo, fcd)
     args = _toolstr(repo.ui, tool, b"args")
 
     with _maketempfiles(
         repo, fco, fca, repo.wvfs.join(backup.path()), b"$output" in args
     ) as temppaths:
         basepath, otherpath, localoutputpath = temppaths
         outpath = b""
         mylabel, otherlabel = labels[:2]
         if len(labels) >= 3:
             baselabel = labels[2]
         else:
             baselabel = b'base'
         env = {
             b'HG_FILE': fcd.path(),
             b'HG_MY_NODE': short(mynode),
             b'HG_OTHER_NODE': short(fco.changectx().node()),
             b'HG_BASE_NODE': short(fca.changectx().node()),
             b'HG_MY_ISLINK': b'l' in fcd.flags(),
             b'HG_OTHER_ISLINK': b'l' in fco.flags(),
             b'HG_BASE_ISLINK': b'l' in fca.flags(),
             b'HG_MY_LABEL': mylabel,
             b'HG_OTHER_LABEL': otherlabel,
             b'HG_BASE_LABEL': baselabel,
         }
         ui = repo.ui
 
         if b"$output" in args:
             # read input from backup, write to original
             outpath = localpath
             localpath = localoutputpath
         replace = {
             b'local': localpath,
             b'base': basepath,
             b'other': otherpath,
             b'output': outpath,
             b'labellocal': mylabel,
             b'labelother': otherlabel,
             b'labelbase': baselabel,
         }
         args = util.interpolate(
             br'\$',
             replace,
             args,
             lambda s: procutil.shellquote(util.localpath(s)),
         )
         if _toolbool(ui, tool, b"gui"):
             repo.ui.status(
                 _(b'running merge tool %s for file %s\n')
                 % (tool, uipathfn(fcd.path()))
             )
         if scriptfn is None:
             cmd = toolpath + b' ' + args
             repo.ui.debug(b'launching merge tool: %s\n' % cmd)
             _describemerge(ui, repo, mynode, fcd, fca, fco, env, toolpath, args)
             r = ui.system(
                 cmd, cwd=repo.root, environ=env, blockedtag=b'mergetool'
             )
         else:
             repo.ui.debug(
                 b'launching python merge script: %s:%s\n' % (toolpath, scriptfn)
             )
             r = 0
             try:
                 # avoid cycle cmdutil->merge->filemerge->extensions->cmdutil
                 from . import extensions
 
                 mod = extensions.loadpath(toolpath, b'hgmerge.%s' % tool)
             except Exception:
                 raise error.Abort(
                     _(b"loading python merge script failed: %s") % toolpath
                 )
             mergefn = getattr(mod, scriptfn, None)
             if mergefn is None:
                 raise error.Abort(
                     _(b"%s does not have function: %s") % (toolpath, scriptfn)
                 )
             argslist = procutil.shellsplit(args)
             # avoid cycle cmdutil->merge->filemerge->hook->extensions->cmdutil
             from . import hook
 
             ret, raised = hook.pythonhook(
                 ui, repo, b"merge", toolpath, mergefn, {b'args': argslist}, True
             )
             if raised:
                 r = 1
         repo.ui.debug(b'merge tool returned: %d\n' % r)
         return True, r, False
 
 
 def _formatlabel(ctx, template, label, pad):
     """Applies the given template to the ctx, prefixed by the label.
 
     Pad is the minimum width of the label prefix, so that multiple markers
     can have aligned templated parts.
     """
     if ctx.node() is None:
         ctx = ctx.p1()
 
     props = {b'ctx': ctx}
     templateresult = template.renderdefault(props)
 
     label = (b'%s:' % label).ljust(pad + 1)
     mark = b'%s %s' % (label, templateresult)
     mark = mark.splitlines()[0]  # split for safety
 
     # 8 for the prefix of conflict marker lines (e.g. '<<<<<<< ')
     return stringutil.ellipsis(mark, 80 - 8)
 
 
 _defaultconflictlabels = [b'local', b'other']
 
 
 def _formatlabels(repo, fcd, fco, fca, labels, tool=None):
     """Formats the given labels using the conflict marker template.
 
     Returns a list of formatted labels.
     """
     cd = fcd.changectx()
     co = fco.changectx()
     ca = fca.changectx()
 
     ui = repo.ui
     template = ui.config(b'command-templates', b'mergemarker')
     if tool is not None:
         template = _toolstr(ui, tool, b'mergemarkertemplate', template)
     template = templater.unquotestring(template)
     tres = formatter.templateresources(ui, repo)
     tmpl = formatter.maketemplater(
         ui, template, defaults=templatekw.keywords, resources=tres
     )
 
     pad = max(len(l) for l in labels)
 
     newlabels = [
         _formatlabel(cd, tmpl, labels[0], pad),
         _formatlabel(co, tmpl, labels[1], pad),
     ]
     if len(labels) > 2:
         newlabels.append(_formatlabel(ca, tmpl, labels[2], pad))
     return newlabels
 
 
 def partextras(labels):
     """Return a dictionary of extra labels for use in prompts to the user
 
     Intended use is in strings of the form "(l)ocal%(l)s".
     """
     if labels is None:
         return {
             b"l": b"",
             b"o": b"",
         }
 
     return {
         b"l": b" [%s]" % labels[0],
         b"o": b" [%s]" % labels[1],
     }
 
 
 def _restorebackup(fcd, backup):
     # TODO: Add a workingfilectx.write(otherfilectx) path so we can use
     # util.copy here instead.
     fcd.write(backup.data(), fcd.flags())
 
 
 def _makebackup(repo, ui, wctx, fcd):
     """Makes and returns a filectx-like object for ``fcd``'s backup file.
 
     In addition to preserving the user's pre-existing modifications to `fcd`
     (if any), the backup is used to undo certain premerges, confirm whether a
     merge changed anything, and determine what line endings the new file should
     have.
 
     Backups only need to be written once since their content doesn't change
     afterwards.
     """
     if fcd.isabsent():
         return None
     # TODO: Break this import cycle somehow. (filectx -> ctx -> fileset ->
     # merge -> filemerge). (I suspect the fileset import is the weakest link)
     from . import context
 
     backup = scmutil.backuppath(ui, repo, fcd.path())
     inworkingdir = backup.startswith(repo.wvfs.base) and not backup.startswith(
         repo.vfs.base
     )
     if isinstance(fcd, context.overlayworkingfilectx) and inworkingdir:
         # If the backup file is to be in the working directory, and we're
         # merging in-memory, we must redirect the backup to the memory context
         # so we don't disturb the working directory.
         relpath = backup[len(repo.wvfs.base) + 1 :]
         wctx[relpath].write(fcd.data(), fcd.flags())
         return wctx[relpath]
     else:
         # Otherwise, write to wherever path the user specified the backups
         # should go. We still need to switch based on whether the source is
         # in-memory so we can use the fast path of ``util.copy`` if both are
         # on disk.
         if isinstance(fcd, context.overlayworkingfilectx):
             util.writefile(backup, fcd.data())
         else:
             a = _workingpath(repo, fcd)
             util.copyfile(a, backup)
         # A arbitraryfilectx is returned, so we can run the same functions on
         # the backup context regardless of where it lives.
         return context.arbitraryfilectx(backup, repo=repo)
 
 
 @contextlib.contextmanager
 def _maketempfiles(repo, fco, fca, localpath, uselocalpath):
     """Writes out `fco` and `fca` as temporary files, and (if uselocalpath)
     copies `localpath` to another temporary file, so an external merge tool may
     use them.
     """
     tmproot = None
     tmprootprefix = repo.ui.config(b'experimental', b'mergetempdirprefix')
     if tmprootprefix:
         tmproot = pycompat.mkdtemp(prefix=tmprootprefix)
 
     def maketempfrompath(prefix, path):
         fullbase, ext = os.path.splitext(path)
         pre = b"%s~%s" % (os.path.basename(fullbase), prefix)
         if tmproot:
             name = os.path.join(tmproot, pre)
             if ext:
                 name += ext
             f = open(name, "wb")
         else:
             fd, name = pycompat.mkstemp(prefix=pre + b'.', suffix=ext)
             f = os.fdopen(fd, "wb")
         return f, name
 
     def tempfromcontext(prefix, ctx):
         f, name = maketempfrompath(prefix, ctx.path())
         data = ctx.decodeddata()
         f.write(data)
         f.close()
         return name
 
     b = tempfromcontext(b"base", fca)
     c = tempfromcontext(b"other", fco)
     d = localpath
     if uselocalpath:
         # We start off with this being the backup filename, so remove the .orig
         # to make syntax-highlighting more likely.
         if d.endswith(b'.orig'):
             d, _ = os.path.splitext(d)
         f, d = maketempfrompath(b"local", d)
         with open(localpath, b'rb') as src:
             f.write(src.read())
         f.close()
 
     try:
         yield b, c, d
     finally:
         if tmproot:
             shutil.rmtree(tmproot)
         else:
             util.unlink(b)
             util.unlink(c)
             # if not uselocalpath, d is the 'orig'/backup file which we
             # shouldn't delete.
             if d and uselocalpath:
                 util.unlink(d)
 
 
 def filemerge(repo, wctx, mynode, orig, fcd, fco, fca, labels=None):
     """perform a 3-way merge in the working directory
 
     mynode = parent node before merge
     orig = original local filename before merge
     fco = other file context
     fca = ancestor file context
     fcd = local file context for current/destination file
 
     Returns whether the merge is complete, the return value of the merge, and
     a boolean indicating whether the file was deleted from disk."""
 
     if not fco.cmp(fcd):  # files identical?
         return None, False
 
     ui = repo.ui
     fd = fcd.path()
     uipathfn = scmutil.getuipathfn(repo)
     fduipath = uipathfn(fd)
     binary = fcd.isbinary() or fco.isbinary() or fca.isbinary()
     symlink = b'l' in fcd.flags() + fco.flags()
     changedelete = fcd.isabsent() or fco.isabsent()
     tool, toolpath = _picktool(repo, ui, fd, binary, symlink, changedelete)
     scriptfn = None
     if tool in internals and tool.startswith(b'internal:'):
         # normalize to new-style names (':merge' etc)
         tool = tool[len(b'internal') :]
     if toolpath and toolpath.startswith(b'python:'):
         invalidsyntax = False
         if toolpath.count(b':') >= 2:
             script, scriptfn = toolpath[7:].rsplit(b':', 1)
             if not scriptfn:
                 invalidsyntax = True
             # missing :callable can lead to spliting on windows drive letter
             if b'\\' in scriptfn or b'/' in scriptfn:
                 invalidsyntax = True
         else:
             invalidsyntax = True
         if invalidsyntax:
             raise error.Abort(_(b"invalid 'python:' syntax: %s") % toolpath)
         toolpath = script
     ui.debug(
         b"picked tool '%s' for %s (binary %s symlink %s changedelete %s)\n"
         % (
             tool,
             fduipath,
             pycompat.bytestr(binary),
             pycompat.bytestr(symlink),
             pycompat.bytestr(changedelete),
         )
     )
 
     if tool in internals:
         func = internals[tool]
         mergetype = func.mergetype
         onfailure = func.onfailure
         precheck = func.precheck
         isexternal = False
     else:
         if wctx.isinmemory():
             func = _xmergeimm
         else:
             func = _xmerge
         mergetype = fullmerge
         onfailure = _(b"merging %s failed!\n")
         precheck = None
         isexternal = True
 
     toolconf = tool, toolpath, binary, symlink, scriptfn
 
     if mergetype == nomerge:
         return func(repo, mynode, fcd, fco, fca, toolconf, labels)
 
     if orig != fco.path():
         ui.status(
             _(b"merging %s and %s to %s\n")
             % (uipathfn(orig), uipathfn(fco.path()), fduipath)
         )
     else:
         ui.status(_(b"merging %s\n") % fduipath)
 
     ui.debug(b"my %s other %s ancestor %s\n" % (fcd, fco, fca))
 
     if precheck and not precheck(repo, mynode, fcd, fco, fca, toolconf):
         if onfailure:
             if wctx.isinmemory():
                 raise error.InMemoryMergeConflictsError(
                     b'in-memory merge does not support merge conflicts'
                 )
             ui.warn(onfailure % fduipath)
         return 1, False
 
     backup = _makebackup(repo, ui, wctx, fcd)
     r = 1
     try:
         internalmarkerstyle = ui.config(b'ui', b'mergemarkers')
         if isexternal:
             markerstyle = _toolstr(ui, tool, b'mergemarkers')
         else:
             markerstyle = internalmarkerstyle
 
         if not labels:
             labels = _defaultconflictlabels
         formattedlabels = labels
         if markerstyle != b'basic':
             formattedlabels = _formatlabels(
                 repo, fcd, fco, fca, labels, tool=tool
             )
 
         if mergetype == fullmerge:
             # conflict markers generated by premerge will use 'detailed'
             # settings if either ui.mergemarkers or the tool's mergemarkers
             # setting is 'detailed'. This way tools can have basic labels in
             # space-constrained areas of the UI, but still get full information
             # in conflict markers if premerge is 'keep' or 'keep-merge3'.
             premergelabels = labels
             labeltool = None
             if markerstyle != b'basic':
                 # respect 'tool's mergemarkertemplate (which defaults to
                 # command-templates.mergemarker)
                 labeltool = tool
             if internalmarkerstyle != b'basic' or markerstyle != b'basic':
                 premergelabels = _formatlabels(
                     repo, fcd, fco, fca, premergelabels, tool=labeltool
                 )
 
             r = _premerge(
                 repo, fcd, fco, fca, toolconf, backup, labels=premergelabels
             )
             # we're done if premerge was successful (r is 0)
             if not r:
                 return r, False
 
         needcheck, r, deleted = func(
             repo,
             mynode,
             fcd,
             fco,
             fca,
             toolconf,
             backup,
             labels=formattedlabels,
         )
 
         if needcheck:
             r = _check(repo, r, ui, tool, fcd, backup)
 
         if r:
             if onfailure:
                 if wctx.isinmemory():
                     raise error.InMemoryMergeConflictsError(
                         b'in-memory merge '
                         b'does not support '
                         b'merge conflicts'
                     )
                 ui.warn(onfailure % fduipath)
             _onfilemergefailure(ui)
 
         return r, deleted
     finally:
         if not r and backup is not None:
             backup.remove()
 
 
 def _haltmerge():
     msg = _(b'merge halted after failed merge (see hg resolve)')
     raise error.InterventionRequired(msg)
 
 
 def _onfilemergefailure(ui):
     action = ui.config(b'merge', b'on-failure')
     if action == b'prompt':
         msg = _(b'continue merge operation (yn)?$$ &Yes $$ &No')
         if ui.promptchoice(msg, 0) == 1:
             _haltmerge()
     if action == b'halt':
         _haltmerge()
     # default action is 'continue', in which case we neither prompt nor halt
 
 
 def hasconflictmarkers(data):
     # Detect lines starting with a string of 7 identical characters from the
     # subset Mercurial uses for conflict markers, followed by either the end of
     # line or a space and some text. Note that using [<>=+|-]{7} would detect
     # `<><><><><` as a conflict marker, which we don't want.
     return bool(
         re.search(
             br"^([<>=+|-])\1{6}( .*)$",
             data,
             re.MULTILINE,
         )
     )
 
 
 def _check(repo, r, ui, tool, fcd, backup):
     fd = fcd.path()
     uipathfn = scmutil.getuipathfn(repo)
 
     if not r and (
         _toolbool(ui, tool, b"checkconflicts")
         or b'conflicts' in _toollist(ui, tool, b"check")
     ):
         if hasconflictmarkers(fcd.data()):
             r = 1
 
     checked = False
     if b'prompt' in _toollist(ui, tool, b"check"):
         checked = True
         if ui.promptchoice(
             _(b"was merge of '%s' successful (yn)?$$ &Yes $$ &No")
             % uipathfn(fd),
             1,
         ):
             r = 1
 
     if (
         not r
         and not checked
         and (
             _toolbool(ui, tool, b"checkchanged")
             or b'changed' in _toollist(ui, tool, b"check")
         )
     ):
         if backup is not None and not fcd.cmp(backup):
             if ui.promptchoice(
                 _(
                     b" output file %s appears unchanged\n"
                     b"was merge successful (yn)?"
                     b"$$ &Yes $$ &No"
                 )
                 % uipathfn(fd),
                 1,
             ):
                 r = 1
 
     if backup is not None and _toolbool(ui, tool, b"fixeol"):
         _matcheol(_workingpath(repo, fcd), backup)
 
     return r
 
 
 def _workingpath(repo, ctx):
     return repo.wjoin(ctx.path())
 
 
 def loadinternalmerge(ui, extname, registrarobj):
     """Load internal merge tool from specified registrarobj"""
     for name, func in pycompat.iteritems(registrarobj._table):
         fullname = b':' + name
         internals[fullname] = func
         internals[b'internal:' + name] = func
         internalsdoc[fullname] = func
 
         capabilities = sorted([k for k, v in func.capabilities.items() if v])
         if capabilities:
             capdesc = b"    (actual capabilities: %s)" % b', '.join(
                 capabilities
             )
             func.__doc__ = func.__doc__ + pycompat.sysstr(b"\n\n%s" % capdesc)
 
     # to put i18n comments into hg.pot for automatically generated texts
 
     # i18n: "binary" and "symlink" are keywords
     # i18n: this text is added automatically
     _(b"    (actual capabilities: binary, symlink)")
     # i18n: "binary" is keyword
     # i18n: this text is added automatically
     _(b"    (actual capabilities: binary)")
     # i18n: "symlink" is keyword
     # i18n: this text is added automatically
     _(b"    (actual capabilities: symlink)")
 
 
 # load built-in merge tools explicitly to setup internalsdoc
 loadinternalmerge(None, None, internaltool)
 
 # tell hggettext to extract docstrings from these functions:
 i18nfunctions = internals.values()

mercurial/simplemerge.py

@@ -1,514 +1,524 b''
 # Copyright (C) 2004, 2005 Canonical Ltd
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program; if not, see <http://www.gnu.org/licenses/>.
 
 # mbp: "you know that thing where cvs gives you conflict markers?"
 # s: "i hate that."
 
 from __future__ import absolute_import
 
 from .i18n import _
+from .thirdparty import attr
 from . import (
     error,
     mdiff,
     pycompat,
 )
 from .utils import stringutil
 
 
 def intersect(ra, rb):
     """Given two ranges return the range where they intersect or None.
 
     >>> intersect((0, 10), (0, 6))
     (0, 6)
     >>> intersect((0, 10), (5, 15))
     (5, 10)
     >>> intersect((0, 10), (10, 15))
     >>> intersect((0, 9), (10, 15))
     >>> intersect((0, 9), (7, 15))
     (7, 9)
     """
     assert ra[0] <= ra[1]
     assert rb[0] <= rb[1]
 
     sa = max(ra[0], rb[0])
     sb = min(ra[1], rb[1])
     if sa < sb:
         return sa, sb
     else:
         return None
 
 
 def compare_range(a, astart, aend, b, bstart, bend):
     """Compare a[astart:aend] == b[bstart:bend], without slicing."""
     if (aend - astart) != (bend - bstart):
         return False
     for ia, ib in zip(
         pycompat.xrange(astart, aend), pycompat.xrange(bstart, bend)
     ):
         if a[ia] != b[ib]:
             return False
     else:
         return True
 
 
 class Merge3Text(object):
     """3-way merge of texts.
 
     Given strings BASE, OTHER, THIS, tries to produce a combined text
     incorporating the changes from both BASE->OTHER and BASE->THIS."""
 
     def __init__(self, basetext, atext, btext, base=None, a=None, b=None):
         self.basetext = basetext
         self.atext = atext
         self.btext = btext
         if base is None:
             base = mdiff.splitnewlines(basetext)
         if a is None:
             a = mdiff.splitnewlines(atext)
         if b is None:
             b = mdiff.splitnewlines(btext)
         self.base = base
         self.a = a
         self.b = b
 
     def merge_groups(self):
         """Yield sequence of line groups.  Each one is a tuple:
 
         'unchanged', lines
              Lines unchanged from base
 
         'a', lines
              Lines taken from a
 
         'same', lines
              Lines taken from a (and equal to b)
 
         'b', lines
              Lines taken from b
 
         'conflict', (base_lines, a_lines, b_lines)
              Lines from base were changed to either a or b and conflict.
         """
         for t in self.merge_regions():
             what = t[0]
             if what == b'unchanged':
                 yield what, self.base[t[1] : t[2]]
             elif what == b'a' or what == b'same':
                 yield what, self.a[t[1] : t[2]]
             elif what == b'b':
                 yield what, self.b[t[1] : t[2]]
             elif what == b'conflict':
                 yield (
                     what,
                     (
                         self.base[t[1] : t[2]],
                         self.a[t[3] : t[4]],
                         self.b[t[5] : t[6]],
                     ),
                 )
             else:
                 raise ValueError(what)
 
     def merge_regions(self):
         """Return sequences of matching and conflicting regions.
 
         This returns tuples, where the first value says what kind we
         have:
 
         'unchanged', start, end
              Take a region of base[start:end]
 
         'same', astart, aend
              b and a are different from base but give the same result
 
         'a', start, end
              Non-clashing insertion from a[start:end]
 
         'conflict', zstart, zend, astart, aend, bstart, bend
             Conflict between a and b, with z as common ancestor
 
         Method is as follows:
 
         The two sequences align only on regions which match the base
         and both descendants.  These are found by doing a two-way diff
         of each one against the base, and then finding the
         intersections between those regions.  These "sync regions"
         are by definition unchanged in both and easily dealt with.
 
         The regions in between can be in any of three cases:
         conflicted, or changed on only one side.
         """
 
         # section a[0:ia] has been disposed of, etc
         iz = ia = ib = 0
 
         for region in self.find_sync_regions():
             zmatch, zend, amatch, aend, bmatch, bend = region
             # print 'match base [%d:%d]' % (zmatch, zend)
 
             matchlen = zend - zmatch
             assert matchlen >= 0
             assert matchlen == (aend - amatch)
             assert matchlen == (bend - bmatch)
 
             len_a = amatch - ia
             len_b = bmatch - ib
             len_base = zmatch - iz
             assert len_a >= 0
             assert len_b >= 0
             assert len_base >= 0
 
             # print 'unmatched a=%d, b=%d' % (len_a, len_b)
 
             if len_a or len_b:
                 # try to avoid actually slicing the lists
                 equal_a = compare_range(
                     self.a, ia, amatch, self.base, iz, zmatch
                 )
                 equal_b = compare_range(
                     self.b, ib, bmatch, self.base, iz, zmatch
                 )
                 same = compare_range(self.a, ia, amatch, self.b, ib, bmatch)
 
                 if same:
                     yield b'same', ia, amatch
                 elif equal_a and not equal_b:
                     yield b'b', ib, bmatch
                 elif equal_b and not equal_a:
                     yield b'a', ia, amatch
                 elif not equal_a and not equal_b:
                     yield b'conflict', iz, zmatch, ia, amatch, ib, bmatch
                 else:
                     raise AssertionError(b"can't handle a=b=base but unmatched")
 
                 ia = amatch
                 ib = bmatch
             iz = zmatch
 
             # if the same part of the base was deleted on both sides
             # that's OK, we can just skip it.
 
             if matchlen > 0:
                 assert ia == amatch
                 assert ib == bmatch
                 assert iz == zmatch
 
                 yield b'unchanged', zmatch, zend
                 iz = zend
                 ia = aend
                 ib = bend
 
     def find_sync_regions(self):
         """Return a list of sync regions, where both descendants match the base.
 
         Generates a list of (base1, base2, a1, a2, b1, b2).  There is
         always a zero-length sync region at the end of all the files.
         """
 
         ia = ib = 0
         amatches = mdiff.get_matching_blocks(self.basetext, self.atext)
         bmatches = mdiff.get_matching_blocks(self.basetext, self.btext)
         len_a = len(amatches)
         len_b = len(bmatches)
 
         sl = []
 
         while ia < len_a and ib < len_b:
             abase, amatch, alen = amatches[ia]
             bbase, bmatch, blen = bmatches[ib]
 
             # there is an unconflicted block at i; how long does it
             # extend?  until whichever one ends earlier.
             i = intersect((abase, abase + alen), (bbase, bbase + blen))
             if i:
                 intbase = i[0]
                 intend = i[1]
                 intlen = intend - intbase
 
                 # found a match of base[i[0], i[1]]; this may be less than
                 # the region that matches in either one
                 assert intlen <= alen
                 assert intlen <= blen
                 assert abase <= intbase
                 assert bbase <= intbase
 
                 asub = amatch + (intbase - abase)
                 bsub = bmatch + (intbase - bbase)
                 aend = asub + intlen
                 bend = bsub + intlen
 
                 assert self.base[intbase:intend] == self.a[asub:aend], (
                     self.base[intbase:intend],
                     self.a[asub:aend],
                 )
 
                 assert self.base[intbase:intend] == self.b[bsub:bend]
 
                 sl.append((intbase, intend, asub, aend, bsub, bend))
 
             # advance whichever one ends first in the base text
             if (abase + alen) < (bbase + blen):
                 ia += 1
             else:
                 ib += 1
 
         intbase = len(self.base)
         abase = len(self.a)
         bbase = len(self.b)
         sl.append((intbase, intbase, abase, abase, bbase, bbase))
 
         return sl
 
 
 def _verifytext(text, path, ui, opts):
     """verifies that text is non-binary (unless opts[text] is passed,
     then we just warn)"""
     if stringutil.binary(text):
         msg = _(b"%s looks like a binary file.") % path
         if not opts.get('quiet'):
             ui.warn(_(b'warning: %s\n') % msg)
         if not opts.get('text'):
             raise error.Abort(msg)
     return text
 
 
-def _picklabels(overrides):
-    if len(overrides) > 3:
-        raise error.Abort(_(b"can only specify three labels."))
-    result = [None, None, None]
-    for i, override in enumerate(overrides):
-        result[i] = override
-    return result
+def _format_labels(*inputs):
+    labels = []
+    for input in inputs:
+        if input.label:
+            labels.append(input.label)
+        else:
+            labels.append(None)
+    return labels
 
 
 def _detect_newline(m3):
     if len(m3.a) > 0:
         if m3.a[0].endswith(b'\r\n'):
             return b'\r\n'
         elif m3.a[0].endswith(b'\r'):
             return b'\r'
     return b'\n'
 
 
 def _minimize(a_lines, b_lines):
     """Trim conflict regions of lines where A and B sides match.
 
     Lines where both A and B have made the same changes at the beginning
     or the end of each merge region are eliminated from the conflict
     region and are instead considered the same.
     """
     alen = len(a_lines)
     blen = len(b_lines)
 
     # find matches at the front
     ii = 0
     while ii < alen and ii < blen and a_lines[ii] == b_lines[ii]:
         ii += 1
     startmatches = ii
 
     # find matches at the end
     ii = 0
     while ii < alen and ii < blen and a_lines[-ii - 1] == b_lines[-ii - 1]:
         ii += 1
     endmatches = ii
 
     lines_before = a_lines[:startmatches]
     new_a_lines = a_lines[startmatches : alen - endmatches]
     new_b_lines = b_lines[startmatches : blen - endmatches]
     lines_after = a_lines[alen - endmatches :]
     return lines_before, new_a_lines, new_b_lines, lines_after
 
 
 def render_minimized(
     m3,
     name_a=None,
     name_b=None,
     start_marker=b'<<<<<<<',
     mid_marker=b'=======',
     end_marker=b'>>>>>>>',
 ):
     """Return merge in cvs-like form."""
     newline = _detect_newline(m3)
     conflicts = False
     if name_a:
         start_marker = start_marker + b' ' + name_a
     if name_b:
         end_marker = end_marker + b' ' + name_b
     merge_groups = m3.merge_groups()
     lines = []
     for what, group_lines in merge_groups:
         if what == b'conflict':
             conflicts = True
             base_lines, a_lines, b_lines = group_lines
             minimized = _minimize(a_lines, b_lines)
             lines_before, a_lines, b_lines, lines_after = minimized
             lines.extend(lines_before)
             lines.append(start_marker + newline)
             lines.extend(a_lines)
             lines.append(mid_marker + newline)
             lines.extend(b_lines)
             lines.append(end_marker + newline)
             lines.extend(lines_after)
         else:
             lines.extend(group_lines)
     return lines, conflicts
 
 
 def render_merge3(m3, name_a, name_b, name_base):
     """Render conflicts as 3-way conflict markers."""
     newline = _detect_newline(m3)
     conflicts = False
     lines = []
     for what, group_lines in m3.merge_groups():
         if what == b'conflict':
             base_lines, a_lines, b_lines = group_lines
             conflicts = True
             lines.append(b'<<<<<<< ' + name_a + newline)
             lines.extend(a_lines)
             lines.append(b'||||||| ' + name_base + newline)
             lines.extend(base_lines)
             lines.append(b'=======' + newline)
             lines.extend(b_lines)
             lines.append(b'>>>>>>> ' + name_b + newline)
         else:
             lines.extend(group_lines)
     return lines, conflicts
 
 
 def render_mergediff(m3, name_a, name_b, name_base):
     """Render conflicts as conflict markers with one snapshot and one diff."""
     newline = _detect_newline(m3)
     lines = []
     conflicts = False
     for what, group_lines in m3.merge_groups():
         if what == b'conflict':
             base_lines, a_lines, b_lines = group_lines
             base_text = b''.join(base_lines)
             b_blocks = list(
                 mdiff.allblocks(
                     base_text,
                     b''.join(b_lines),
                     lines1=base_lines,
                     lines2=b_lines,
                 )
             )
             a_blocks = list(
                 mdiff.allblocks(
                     base_text,
                     b''.join(a_lines),
                     lines1=base_lines,
                     lines2=b_lines,
                 )
             )
 
             def matching_lines(blocks):
                 return sum(
                     block[1] - block[0]
                     for block, kind in blocks
                     if kind == b'='
                 )
 
             def diff_lines(blocks, lines1, lines2):
                 for block, kind in blocks:
                     if kind == b'=':
                         for line in lines1[block[0] : block[1]]:
                             yield b' ' + line
                     else:
                         for line in lines1[block[0] : block[1]]:
                             yield b'-' + line
                         for line in lines2[block[2] : block[3]]:
                             yield b'+' + line
 
             lines.append(b"<<<<<<<" + newline)
             if matching_lines(a_blocks) < matching_lines(b_blocks):
                 lines.append(b"======= " + name_a + newline)
                 lines.extend(a_lines)
                 lines.append(b"------- " + name_base + newline)
                 lines.append(b"+++++++ " + name_b + newline)
                 lines.extend(diff_lines(b_blocks, base_lines, b_lines))
             else:
                 lines.append(b"------- " + name_base + newline)
                 lines.append(b"+++++++ " + name_a + newline)
                 lines.extend(diff_lines(a_blocks, base_lines, a_lines))
                 lines.append(b"======= " + name_b + newline)
                 lines.extend(b_lines)
             lines.append(b">>>>>>>" + newline)
             conflicts = True
         else:
             lines.extend(group_lines)
     return lines, conflicts
 
 
 def _resolve(m3, sides):
     lines = []
     for what, group_lines in m3.merge_groups():
         if what == b'conflict':
             for side in sides:
                 lines.extend(group_lines[side])
         else:
             lines.extend(group_lines)
     return lines
 
 
-def simplemerge(ui, localctx, basectx, otherctx, **opts):
+@attr.s
+class MergeInput(object):
+    fctx = attr.ib()
+    label = attr.ib(default=None)
+
+
+def simplemerge(ui, local, base, other, **opts):
     """Performs the simplemerge algorithm.
 
     The merged result is written into `localctx`.
     """
 
     def readctx(ctx):
         # Merges were always run in the working copy before, which means
         # they used decoded data, if the user defined any repository
         # filters.
         #
         # Maintain that behavior today for BC, though perhaps in the future
         # it'd be worth considering whether merging encoded data (what the
         # repository usually sees) might be more useful.
         return _verifytext(ctx.decodeddata(), ctx.path(), ui, opts)
 
     try:
-        localtext = readctx(localctx)
-        basetext = readctx(basectx)
-        othertext = readctx(otherctx)
+        localtext = readctx(local.fctx)
+        basetext = readctx(base.fctx)
+        othertext = readctx(other.fctx)
     except error.Abort:
         return True
 
     m3 = Merge3Text(basetext, localtext, othertext)
     conflicts = False
     mode = opts.get('mode', b'merge')
     if mode == b'union':
         lines = _resolve(m3, (1, 2))
     elif mode == b'local':
         lines = _resolve(m3, (1,))
     elif mode == b'other':
         lines = _resolve(m3, (2,))
     else:
-        name_a, name_b, name_base = _picklabels(opts.get('label', []))
         if mode == b'mergediff':
-            lines, conflicts = render_mergediff(m3, name_a, name_b, name_base)
+            labels = _format_labels(local, other, base)
+            lines, conflicts = render_mergediff(m3, *labels)
         elif mode == b'merge3':
-            lines, conflicts = render_merge3(m3, name_a, name_b, name_base)
+            labels = _format_labels(local, other, base)
+            lines, conflicts = render_merge3(m3, *labels)
         else:
-            lines, conflicts = render_minimized(m3, name_a, name_b)
+            labels = _format_labels(local, other)
+            lines, conflicts = render_minimized(m3, *labels)
 
     mergedtext = b''.join(lines)
     if opts.get('print'):
         ui.fout.write(mergedtext)
     else:
-        # localctx.flags() already has the merged flags (done in
+        # local.fctx.flags() already has the merged flags (done in
         # mergestate.resolve())
-        localctx.write(mergedtext, localctx.flags())
+        local.fctx.write(mergedtext, local.fctx.flags())
 
     return conflicts