fix: rewrite writeworkingdir() to explicitly not work with merges

`hg fix` errors out early if there is an unfinished merge, so we
should have only one parent here. Making that explicit makes my next
patches simpler.

Differential Revision: https://phab.mercurial-scm.org/D11209

hgext/fix.py

@@ -1,940 +1,943 b''
 # fix - rewrite file content in changesets and working copy
 #
 # Copyright 2018 Google LLC.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 """rewrite file content in changesets or working copy (EXPERIMENTAL)
 
 Provides a command that runs configured tools on the contents of modified files,
 writing back any fixes to the working copy or replacing changesets.
 
 Here is an example configuration that causes :hg:`fix` to apply automatic
 formatting fixes to modified lines in C++ code::
 
   [fix]
   clang-format:command=clang-format --assume-filename={rootpath}
   clang-format:linerange=--lines={first}:{last}
   clang-format:pattern=set:**.cpp or **.hpp
 
 The :command suboption forms the first part of the shell command that will be
 used to fix a file. The content of the file is passed on standard input, and the
 fixed file content is expected on standard output. Any output on standard error
 will be displayed as a warning. If the exit status is not zero, the file will
 not be affected. A placeholder warning is displayed if there is a non-zero exit
 status but no standard error output. Some values may be substituted into the
 command::
 
   {rootpath}  The path of the file being fixed, relative to the repo root
   {basename}  The name of the file being fixed, without the directory path
 
 If the :linerange suboption is set, the tool will only be run if there are
 changed lines in a file. The value of this suboption is appended to the shell
 command once for every range of changed lines in the file. Some values may be
 substituted into the command::
 
   {first}   The 1-based line number of the first line in the modified range
   {last}    The 1-based line number of the last line in the modified range
 
 Deleted sections of a file will be ignored by :linerange, because there is no
 corresponding line range in the version being fixed.
 
 By default, tools that set :linerange will only be executed if there is at least
 one changed line range. This is meant to prevent accidents like running a code
 formatter in such a way that it unexpectedly reformats the whole file. If such a
 tool needs to operate on unchanged files, it should set the :skipclean suboption
 to false.
 
 The :pattern suboption determines which files will be passed through each
 configured tool. See :hg:`help patterns` for possible values. However, all
 patterns are relative to the repo root, even if that text says they are relative
 to the current working directory. If there are file arguments to :hg:`fix`, the
 intersection of these patterns is used.
 
 There is also a configurable limit for the maximum size of file that will be
 processed by :hg:`fix`::
 
   [fix]
   maxfilesize = 2MB
 
 Normally, execution of configured tools will continue after a failure (indicated
 by a non-zero exit status). It can also be configured to abort after the first
 such failure, so that no files will be affected if any tool fails. This abort
 will also cause :hg:`fix` to exit with a non-zero status::
 
   [fix]
   failure = abort
 
 When multiple tools are configured to affect a file, they execute in an order
 defined by the :priority suboption. The priority suboption has a default value
 of zero for each tool. Tools are executed in order of descending priority. The
 execution order of tools with equal priority is unspecified. For example, you
 could use the 'sort' and 'head' utilities to keep only the 10 smallest numbers
 in a text file by ensuring that 'sort' runs before 'head'::
 
   [fix]
   sort:command = sort -n
   head:command = head -n 10
   sort:pattern = numbers.txt
   head:pattern = numbers.txt
   sort:priority = 2
   head:priority = 1
 
 To account for changes made by each tool, the line numbers used for incremental
 formatting are recomputed before executing the next tool. So, each tool may see
 different values for the arguments added by the :linerange suboption.
 
 Each fixer tool is allowed to return some metadata in addition to the fixed file
 content. The metadata must be placed before the file content on stdout,
 separated from the file content by a zero byte. The metadata is parsed as a JSON
 value (so, it should be UTF-8 encoded and contain no zero bytes). A fixer tool
 is expected to produce this metadata encoding if and only if the :metadata
 suboption is true::
 
   [fix]
   tool:command = tool --prepend-json-metadata
   tool:metadata = true
 
 The metadata values are passed to hooks, which can be used to print summaries or
 perform other post-fixing work. The supported hooks are::
 
   "postfixfile"
     Run once for each file in each revision where any fixer tools made changes
     to the file content. Provides "$HG_REV" and "$HG_PATH" to identify the file,
     and "$HG_METADATA" with a map of fixer names to metadata values from fixer
     tools that affected the file. Fixer tools that didn't affect the file have a
     value of None. Only fixer tools that executed are present in the metadata.
 
   "postfix"
     Run once after all files and revisions have been handled. Provides
     "$HG_REPLACEMENTS" with information about what revisions were created and
     made obsolete. Provides a boolean "$HG_WDIRWRITTEN" to indicate whether any
     files in the working copy were updated. Provides a list "$HG_METADATA"
     mapping fixer tool names to lists of metadata values returned from
     executions that modified a file. This aggregates the same metadata
     previously passed to the "postfixfile" hook.
 
 Fixer tools are run in the repository's root directory. This allows them to read
 configuration files from the working copy, or even write to the working copy.
 The working copy is not updated to match the revision being fixed. In fact,
 several revisions may be fixed in parallel. Writes to the working copy are not
 amended into the revision being fixed; fixer tools should always write fixed
 file content back to stdout as documented above.
 """
 
 from __future__ import absolute_import
 
 import collections
 import itertools
 import os
 import re
 import subprocess
 
 from mercurial.i18n import _
 from mercurial.node import (
+    nullid,
     nullrev,
     wdirrev,
 )
 
 from mercurial.utils import procutil
 
 from mercurial import (
     cmdutil,
     context,
     copies,
     error,
     match as matchmod,
     mdiff,
     merge,
     mergestate as mergestatemod,
     pycompat,
     registrar,
     rewriteutil,
     scmutil,
     util,
     worker,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = b'ships-with-hg-core'
 
 cmdtable = {}
 command = registrar.command(cmdtable)
 
 configtable = {}
 configitem = registrar.configitem(configtable)
 
 # Register the suboptions allowed for each configured fixer, and default values.
 FIXER_ATTRS = {
     b'command': None,
     b'linerange': None,
     b'pattern': None,
     b'priority': 0,
     b'metadata': False,
     b'skipclean': True,
     b'enabled': True,
 }
 
 for key, default in FIXER_ATTRS.items():
     configitem(b'fix', b'.*:%s$' % key, default=default, generic=True)
 
 # A good default size allows most source code files to be fixed, but avoids
 # letting fixer tools choke on huge inputs, which could be surprising to the
 # user.
 configitem(b'fix', b'maxfilesize', default=b'2MB')
 
 # Allow fix commands to exit non-zero if an executed fixer tool exits non-zero.
 # This helps users do shell scripts that stop when a fixer tool signals a
 # problem.
 configitem(b'fix', b'failure', default=b'continue')
 
 
 def checktoolfailureaction(ui, message, hint=None):
     """Abort with 'message' if fix.failure=abort"""
     action = ui.config(b'fix', b'failure')
     if action not in (b'continue', b'abort'):
         raise error.Abort(
             _(b'unknown fix.failure action: %s') % (action,),
             hint=_(b'use "continue" or "abort"'),
         )
     if action == b'abort':
         raise error.Abort(message, hint=hint)
 
 
 allopt = (b'', b'all', False, _(b'fix all non-public non-obsolete revisions'))
 baseopt = (
     b'',
     b'base',
     [],
     _(
         b'revisions to diff against (overrides automatic '
         b'selection, and applies to every revision being '
         b'fixed)'
     ),
     _(b'REV'),
 )
 revopt = (b'r', b'rev', [], _(b'revisions to fix (ADVANCED)'), _(b'REV'))
 sourceopt = (
     b's',
     b'source',
     [],
     _(b'fix the specified revisions and their descendants'),
     _(b'REV'),
 )
 wdiropt = (b'w', b'working-dir', False, _(b'fix the working directory'))
 wholeopt = (b'', b'whole', False, _(b'always fix every line of a file'))
 usage = _(b'[OPTION]... [FILE]...')
 
 
 @command(
     b'fix',
     [allopt, baseopt, revopt, sourceopt, wdiropt, wholeopt],
     usage,
     helpcategory=command.CATEGORY_FILE_CONTENTS,
 )
 def fix(ui, repo, *pats, **opts):
     """rewrite file content in changesets or working directory
 
     Runs any configured tools to fix the content of files. Only affects files
     with changes, unless file arguments are provided. Only affects changed lines
     of files, unless the --whole flag is used. Some tools may always affect the
     whole file regardless of --whole.
 
     If --working-dir is used, files with uncommitted changes in the working copy
     will be fixed. Note that no backup are made.
 
     If revisions are specified with --source, those revisions and their
     descendants will be checked, and they may be replaced with new revisions
     that have fixed file content. By automatically including the descendants,
     no merging, rebasing, or evolution will be required. If an ancestor of the
     working copy is included, then the working copy itself will also be fixed,
     and the working copy will be updated to the fixed parent.
 
     When determining what lines of each file to fix at each revision, the whole
     set of revisions being fixed is considered, so that fixes to earlier
     revisions are not forgotten in later ones. The --base flag can be used to
     override this default behavior, though it is not usually desirable to do so.
     """
     opts = pycompat.byteskwargs(opts)
     cmdutil.check_at_most_one_arg(opts, b'all', b'source', b'rev')
     cmdutil.check_incompatible_arguments(
         opts, b'working_dir', [b'all', b'source']
     )
 
     with repo.wlock(), repo.lock(), repo.transaction(b'fix'):
         revstofix = getrevstofix(ui, repo, opts)
         basectxs = getbasectxs(repo, opts, revstofix)
         workqueue, numitems = getworkqueue(
             ui, repo, pats, opts, revstofix, basectxs
         )
         basepaths = getbasepaths(repo, opts, workqueue, basectxs)
         fixers = getfixers(ui)
 
         # Rather than letting each worker independently fetch the files
         # (which also would add complications for shared/keepalive
         # connections), prefetch them all first.
         _prefetchfiles(repo, workqueue, basepaths)
 
         # There are no data dependencies between the workers fixing each file
         # revision, so we can use all available parallelism.
         def getfixes(items):
             for rev, path in items:
                 ctx = repo[rev]
                 olddata = ctx[path].data()
                 metadata, newdata = fixfile(
                     ui, repo, opts, fixers, ctx, path, basepaths, basectxs[rev]
                 )
                 # Don't waste memory/time passing unchanged content back, but
                 # produce one result per item either way.
                 yield (
                     rev,
                     path,
                     metadata,
                     newdata if newdata != olddata else None,
                 )
 
         results = worker.worker(
             ui, 1.0, getfixes, tuple(), workqueue, threadsafe=False
         )
 
         # We have to hold on to the data for each successor revision in memory
         # until all its parents are committed. We ensure this by committing and
         # freeing memory for the revisions in some topological order. This
         # leaves a little bit of memory efficiency on the table, but also makes
         # the tests deterministic. It might also be considered a feature since
         # it makes the results more easily reproducible.
         filedata = collections.defaultdict(dict)
         aggregatemetadata = collections.defaultdict(list)
         replacements = {}
         wdirwritten = False
         commitorder = sorted(revstofix, reverse=True)
         with ui.makeprogress(
             topic=_(b'fixing'), unit=_(b'files'), total=sum(numitems.values())
         ) as progress:
             for rev, path, filerevmetadata, newdata in results:
                 progress.increment(item=path)
                 for fixername, fixermetadata in filerevmetadata.items():
                     aggregatemetadata[fixername].append(fixermetadata)
                 if newdata is not None:
                     filedata[rev][path] = newdata
                     hookargs = {
                         b'rev': rev,
                         b'path': path,
                         b'metadata': filerevmetadata,
                     }
                     repo.hook(
                         b'postfixfile',
                         throw=False,
                         **pycompat.strkwargs(hookargs)
                     )
                 numitems[rev] -= 1
                 # Apply the fixes for this and any other revisions that are
                 # ready and sitting at the front of the queue. Using a loop here
                 # prevents the queue from being blocked by the first revision to
                 # be ready out of order.
                 while commitorder and not numitems[commitorder[-1]]:
                     rev = commitorder.pop()
                     ctx = repo[rev]
                     if rev == wdirrev:
                         writeworkingdir(repo, ctx, filedata[rev], replacements)
                         wdirwritten = bool(filedata[rev])
                     else:
                         replacerev(ui, repo, ctx, filedata[rev], replacements)
                     del filedata[rev]
 
         cleanup(repo, replacements, wdirwritten)
         hookargs = {
             b'replacements': replacements,
             b'wdirwritten': wdirwritten,
             b'metadata': aggregatemetadata,
         }
         repo.hook(b'postfix', throw=True, **pycompat.strkwargs(hookargs))
 
 
 def cleanup(repo, replacements, wdirwritten):
     """Calls scmutil.cleanupnodes() with the given replacements.
 
     "replacements" is a dict from nodeid to nodeid, with one key and one value
     for every revision that was affected by fixing. This is slightly different
     from cleanupnodes().
 
     "wdirwritten" is a bool which tells whether the working copy was affected by
     fixing, since it has no entry in "replacements".
 
     Useful as a hook point for extending "hg fix" with output summarizing the
     effects of the command, though we choose not to output anything here.
     """
     replacements = {
         prec: [succ] for prec, succ in pycompat.iteritems(replacements)
     }
     scmutil.cleanupnodes(repo, replacements, b'fix', fixphase=True)
 
 
 def getworkqueue(ui, repo, pats, opts, revstofix, basectxs):
     """Constructs the list of files to be fixed at specific revisions
 
     It is up to the caller how to consume the work items, and the only
     dependence between them is that replacement revisions must be committed in
     topological order. Each work item represents a file in the working copy or
     in some revision that should be fixed and written back to the working copy
     or into a replacement revision.
 
     Work items for the same revision are grouped together, so that a worker
     pool starting with the first N items in parallel is likely to finish the
     first revision's work before other revisions. This can allow us to write
     the result to disk and reduce memory footprint. At time of writing, the
     partition strategy in worker.py seems favorable to this. We also sort the
     items by ascending revision number to match the order in which we commit
     the fixes later.
     """
     workqueue = []
     numitems = collections.defaultdict(int)
     maxfilesize = ui.configbytes(b'fix', b'maxfilesize')
     for rev in sorted(revstofix):
         fixctx = repo[rev]
         match = scmutil.match(fixctx, pats, opts)
         for path in sorted(
             pathstofix(ui, repo, pats, opts, match, basectxs[rev], fixctx)
         ):
             fctx = fixctx[path]
             if fctx.islink():
                 continue
             if fctx.size() > maxfilesize:
                 ui.warn(
                     _(b'ignoring file larger than %s: %s\n')
                     % (util.bytecount(maxfilesize), path)
                 )
                 continue
             workqueue.append((rev, path))
             numitems[rev] += 1
     return workqueue, numitems
 
 
 def getrevstofix(ui, repo, opts):
     """Returns the set of revision numbers that should be fixed"""
     if opts[b'all']:
         revs = repo.revs(b'(not public() and not obsolete()) or wdir()')
     elif opts[b'source']:
         source_revs = scmutil.revrange(repo, opts[b'source'])
         revs = set(repo.revs(b'(%ld::) - obsolete()', source_revs))
         if wdirrev in source_revs:
             # `wdir()::` is currently empty, so manually add wdir
             revs.add(wdirrev)
         if repo[b'.'].rev() in revs:
             revs.add(wdirrev)
     else:
         revs = set(scmutil.revrange(repo, opts[b'rev']))
         if opts.get(b'working_dir'):
             revs.add(wdirrev)
         for rev in revs:
             checkfixablectx(ui, repo, repo[rev])
     # Allow fixing only wdir() even if there's an unfinished operation
     if not (len(revs) == 1 and wdirrev in revs):
         cmdutil.checkunfinished(repo)
         rewriteutil.precheck(repo, revs, b'fix')
     if (
         wdirrev in revs
         and mergestatemod.mergestate.read(repo).unresolvedcount()
     ):
         raise error.Abort(b'unresolved conflicts', hint=b"use 'hg resolve'")
     if not revs:
         raise error.Abort(
             b'no changesets specified', hint=b'use --source or --working-dir'
         )
     return revs
 
 
 def checkfixablectx(ui, repo, ctx):
     """Aborts if the revision shouldn't be replaced with a fixed one."""
     if ctx.obsolete():
         # It would be better to actually check if the revision has a successor.
         allowdivergence = ui.configbool(
             b'experimental', b'evolution.allowdivergence'
         )
         if not allowdivergence:
             raise error.Abort(
                 b'fixing obsolete revision could cause divergence'
             )
 
 
 def pathstofix(ui, repo, pats, opts, match, basectxs, fixctx):
     """Returns the set of files that should be fixed in a context
 
     The result depends on the base contexts; we include any file that has
     changed relative to any of the base contexts. Base contexts should be
     ancestors of the context being fixed.
     """
     files = set()
     for basectx in basectxs:
         stat = basectx.status(
             fixctx, match=match, listclean=bool(pats), listunknown=bool(pats)
         )
         files.update(
             set(
                 itertools.chain(
                     stat.added, stat.modified, stat.clean, stat.unknown
                 )
             )
         )
     return files
 
 
 def lineranges(opts, path, basepaths, basectxs, fixctx, content2):
     """Returns the set of line ranges that should be fixed in a file
 
     Of the form [(10, 20), (30, 40)].
 
     This depends on the given base contexts; we must consider lines that have
     changed versus any of the base contexts, and whether the file has been
     renamed versus any of them.
 
     Another way to understand this is that we exclude line ranges that are
     common to the file in all base contexts.
     """
     if opts.get(b'whole'):
         # Return a range containing all lines. Rely on the diff implementation's
         # idea of how many lines are in the file, instead of reimplementing it.
         return difflineranges(b'', content2)
 
     rangeslist = []
     for basectx in basectxs:
         basepath = basepaths.get((basectx.rev(), fixctx.rev(), path), path)
 
         if basepath in basectx:
             content1 = basectx[basepath].data()
         else:
             content1 = b''
         rangeslist.extend(difflineranges(content1, content2))
     return unionranges(rangeslist)
 
 
 def getbasepaths(repo, opts, workqueue, basectxs):
     if opts.get(b'whole'):
         # Base paths will never be fetched for line range determination.
         return {}
 
     basepaths = {}
     for rev, path in workqueue:
         fixctx = repo[rev]
         for basectx in basectxs[rev]:
             basepath = copies.pathcopies(basectx, fixctx).get(path, path)
             if basepath in basectx:
                 basepaths[(basectx.rev(), fixctx.rev(), path)] = basepath
     return basepaths
 
 
 def unionranges(rangeslist):
     """Return the union of some closed intervals
 
     >>> unionranges([])
     []
     >>> unionranges([(1, 100)])
     [(1, 100)]
     >>> unionranges([(1, 100), (1, 100)])
     [(1, 100)]
     >>> unionranges([(1, 100), (2, 100)])
     [(1, 100)]
     >>> unionranges([(1, 99), (1, 100)])
     [(1, 100)]
     >>> unionranges([(1, 100), (40, 60)])
     [(1, 100)]
     >>> unionranges([(1, 49), (50, 100)])
     [(1, 100)]
     >>> unionranges([(1, 48), (50, 100)])
     [(1, 48), (50, 100)]
     >>> unionranges([(1, 2), (3, 4), (5, 6)])
     [(1, 6)]
     """
     rangeslist = sorted(set(rangeslist))
     unioned = []
     if rangeslist:
         unioned, rangeslist = [rangeslist[0]], rangeslist[1:]
     for a, b in rangeslist:
         c, d = unioned[-1]
         if a > d + 1:
             unioned.append((a, b))
         else:
             unioned[-1] = (c, max(b, d))
     return unioned
 
 
 def difflineranges(content1, content2):
     """Return list of line number ranges in content2 that differ from content1.
 
     Line numbers are 1-based. The numbers are the first and last line contained
     in the range. Single-line ranges have the same line number for the first and
     last line. Excludes any empty ranges that result from lines that are only
     present in content1. Relies on mdiff's idea of where the line endings are in
     the string.
 
     >>> from mercurial import pycompat
     >>> lines = lambda s: b'\\n'.join([c for c in pycompat.iterbytestr(s)])
     >>> difflineranges2 = lambda a, b: difflineranges(lines(a), lines(b))
     >>> difflineranges2(b'', b'')
     []
     >>> difflineranges2(b'a', b'')
     []
     >>> difflineranges2(b'', b'A')
     [(1, 1)]
     >>> difflineranges2(b'a', b'a')
     []
     >>> difflineranges2(b'a', b'A')
     [(1, 1)]
     >>> difflineranges2(b'ab', b'')
     []
     >>> difflineranges2(b'', b'AB')
     [(1, 2)]
     >>> difflineranges2(b'abc', b'ac')
     []
     >>> difflineranges2(b'ab', b'aCb')
     [(2, 2)]
     >>> difflineranges2(b'abc', b'aBc')
     [(2, 2)]
     >>> difflineranges2(b'ab', b'AB')
     [(1, 2)]
     >>> difflineranges2(b'abcde', b'aBcDe')
     [(2, 2), (4, 4)]
     >>> difflineranges2(b'abcde', b'aBCDe')
     [(2, 4)]
     """
     ranges = []
     for lines, kind in mdiff.allblocks(content1, content2):
         firstline, lastline = lines[2:4]
         if kind == b'!' and firstline != lastline:
             ranges.append((firstline + 1, lastline))
     return ranges
 
 
 def getbasectxs(repo, opts, revstofix):
     """Returns a map of the base contexts for each revision
 
     The base contexts determine which lines are considered modified when we
     attempt to fix just the modified lines in a file. It also determines which
     files we attempt to fix, so it is important to compute this even when
     --whole is used.
     """
     # The --base flag overrides the usual logic, and we give every revision
     # exactly the set of baserevs that the user specified.
     if opts.get(b'base'):
         baserevs = set(scmutil.revrange(repo, opts.get(b'base')))
         if not baserevs:
             baserevs = {nullrev}
         basectxs = {repo[rev] for rev in baserevs}
         return {rev: basectxs for rev in revstofix}
 
     # Proceed in topological order so that we can easily determine each
     # revision's baserevs by looking at its parents and their baserevs.
     basectxs = collections.defaultdict(set)
     for rev in sorted(revstofix):
         ctx = repo[rev]
         for pctx in ctx.parents():
             if pctx.rev() in basectxs:
                 basectxs[rev].update(basectxs[pctx.rev()])
             else:
                 basectxs[rev].add(pctx)
     return basectxs
 
 
 def _prefetchfiles(repo, workqueue, basepaths):
     toprefetch = set()
 
     # Prefetch the files that will be fixed.
     for rev, path in workqueue:
         if rev == wdirrev:
             continue
         toprefetch.add((rev, path))
 
     # Prefetch the base contents for lineranges().
     for (baserev, fixrev, path), basepath in basepaths.items():
         toprefetch.add((baserev, basepath))
 
     if toprefetch:
         scmutil.prefetchfiles(
             repo,
             [
                 (rev, scmutil.matchfiles(repo, [path]))
                 for rev, path in toprefetch
             ],
         )
 
 
 def fixfile(ui, repo, opts, fixers, fixctx, path, basepaths, basectxs):
     """Run any configured fixers that should affect the file in this context
 
     Returns the file content that results from applying the fixers in some order
     starting with the file's content in the fixctx. Fixers that support line
     ranges will affect lines that have changed relative to any of the basectxs
     (i.e. they will only avoid lines that are common to all basectxs).
 
     A fixer tool's stdout will become the file's new content if and only if it
     exits with code zero. The fixer tool's working directory is the repository's
     root.
     """
     metadata = {}
     newdata = fixctx[path].data()
     for fixername, fixer in pycompat.iteritems(fixers):
         if fixer.affects(opts, fixctx, path):
             ranges = lineranges(
                 opts, path, basepaths, basectxs, fixctx, newdata
             )
             command = fixer.command(ui, path, ranges)
             if command is None:
                 continue
             ui.debug(b'subprocess: %s\n' % (command,))
             proc = subprocess.Popen(
                 procutil.tonativestr(command),
                 shell=True,
                 cwd=procutil.tonativestr(repo.root),
                 stdin=subprocess.PIPE,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,
             )
             stdout, stderr = proc.communicate(newdata)
             if stderr:
                 showstderr(ui, fixctx.rev(), fixername, stderr)
             newerdata = stdout
             if fixer.shouldoutputmetadata():
                 try:
                     metadatajson, newerdata = stdout.split(b'\0', 1)
                     metadata[fixername] = pycompat.json_loads(metadatajson)
                 except ValueError:
                     ui.warn(
                         _(b'ignored invalid output from fixer tool: %s\n')
                         % (fixername,)
                     )
                     continue
             else:
                 metadata[fixername] = None
             if proc.returncode == 0:
                 newdata = newerdata
             else:
                 if not stderr:
                     message = _(b'exited with status %d\n') % (proc.returncode,)
                     showstderr(ui, fixctx.rev(), fixername, message)
                 checktoolfailureaction(
                     ui,
                     _(b'no fixes will be applied'),
                     hint=_(
                         b'use --config fix.failure=continue to apply any '
                         b'successful fixes anyway'
                     ),
                 )
     return metadata, newdata
 
 
 def showstderr(ui, rev, fixername, stderr):
     """Writes the lines of the stderr string as warnings on the ui
 
     Uses the revision number and fixername to give more context to each line of
     the error message. Doesn't include file names, since those take up a lot of
     space and would tend to be included in the error message if they were
     relevant.
     """
     for line in re.split(b'[\r\n]+', stderr):
         if line:
             ui.warn(b'[')
             if rev is None:
                 ui.warn(_(b'wdir'), label=b'evolve.rev')
             else:
                 ui.warn(b'%d' % rev, label=b'evolve.rev')
             ui.warn(b'] %s: %s\n' % (fixername, line))
 
 
 def writeworkingdir(repo, ctx, filedata, replacements):
     """Write new content to the working copy and check out the new p1 if any
 
     We check out a new revision if and only if we fixed something in both the
     working directory and its parent revision. This avoids the need for a full
     update/merge, and means that the working directory simply isn't affected
     unless the --working-dir flag is given.
 
     Directly updates the dirstate for the affected files.
     """
+    assert repo.dirstate.p2() == nullid
+
     for path, data in pycompat.iteritems(filedata):
         fctx = ctx[path]
         fctx.write(data, fctx.flags())
         if repo.dirstate[path] == b'n':
             repo.dirstate.set_possibly_dirty(path)
 
-    oldparentnodes = repo.dirstate.parents()
-    newparentnodes = [replacements.get(n, n) for n in oldparentnodes]
-    if newparentnodes != oldparentnodes:
-        repo.setparents(*newparentnodes)
+    oldp1 = repo.dirstate.p1()
+    newp1 = replacements.get(oldp1, oldp1)
+    if newp1 != oldp1:
+        repo.setparents(newp1, nullid)
 
 
 def replacerev(ui, repo, ctx, filedata, replacements):
     """Commit a new revision like the given one, but with file content changes
 
     "ctx" is the original revision to be replaced by a modified one.
 
     "filedata" is a dict that maps paths to their new file content. All other
     paths will be recreated from the original revision without changes.
     "filedata" may contain paths that didn't exist in the original revision;
     they will be added.
 
     "replacements" is a dict that maps a single node to a single node, and it is
     updated to indicate the original revision is replaced by the newly created
     one. No entry is added if the replacement's node already exists.
 
     The new revision has the same parents as the old one, unless those parents
     have already been replaced, in which case those replacements are the parents
     of this new revision. Thus, if revisions are replaced in topological order,
     there is no need to rebase them into the original topology later.
     """
 
     p1rev, p2rev = repo.changelog.parentrevs(ctx.rev())
     p1ctx, p2ctx = repo[p1rev], repo[p2rev]
     newp1node = replacements.get(p1ctx.node(), p1ctx.node())
     newp2node = replacements.get(p2ctx.node(), p2ctx.node())
 
     # We don't want to create a revision that has no changes from the original,
     # but we should if the original revision's parent has been replaced.
     # Otherwise, we would produce an orphan that needs no actual human
     # intervention to evolve. We can't rely on commit() to avoid creating the
     # un-needed revision because the extra field added below produces a new hash
     # regardless of file content changes.
     if (
         not filedata
         and p1ctx.node() not in replacements
         and p2ctx.node() not in replacements
     ):
         return
 
     extra = ctx.extra().copy()
     extra[b'fix_source'] = ctx.hex()
 
     wctx = context.overlayworkingctx(repo)
     wctx.setbase(repo[newp1node])
     merge.revert_to(ctx, wc=wctx)
     copies.graftcopies(wctx, ctx, ctx.p1())
 
     for path in filedata.keys():
         fctx = ctx[path]
         copysource = fctx.copysource()
         wctx.write(path, filedata[path], flags=fctx.flags())
         if copysource:
             wctx.markcopied(path, copysource)
 
     desc = rewriteutil.update_hash_refs(
         repo,
         ctx.description(),
         {oldnode: [newnode] for oldnode, newnode in replacements.items()},
     )
 
     memctx = wctx.tomemctx(
         text=desc,
         branch=ctx.branch(),
         extra=extra,
         date=ctx.date(),
         parents=(newp1node, newp2node),
         user=ctx.user(),
     )
 
     sucnode = memctx.commit()
     prenode = ctx.node()
     if prenode == sucnode:
         ui.debug(b'node %s already existed\n' % (ctx.hex()))
     else:
         replacements[ctx.node()] = sucnode
 
 
 def getfixers(ui):
     """Returns a map of configured fixer tools indexed by their names
 
     Each value is a Fixer object with methods that implement the behavior of the
     fixer's config suboptions. Does not validate the config values.
     """
     fixers = {}
     for name in fixernames(ui):
         enabled = ui.configbool(b'fix', name + b':enabled')
         command = ui.config(b'fix', name + b':command')
         pattern = ui.config(b'fix', name + b':pattern')
         linerange = ui.config(b'fix', name + b':linerange')
         priority = ui.configint(b'fix', name + b':priority')
         metadata = ui.configbool(b'fix', name + b':metadata')
         skipclean = ui.configbool(b'fix', name + b':skipclean')
         # Don't use a fixer if it has no pattern configured. It would be
         # dangerous to let it affect all files. It would be pointless to let it
         # affect no files. There is no reasonable subset of files to use as the
         # default.
         if command is None:
             ui.warn(
                 _(b'fixer tool has no command configuration: %s\n') % (name,)
             )
         elif pattern is None:
             ui.warn(
                 _(b'fixer tool has no pattern configuration: %s\n') % (name,)
             )
         elif not enabled:
             ui.debug(b'ignoring disabled fixer tool: %s\n' % (name,))
         else:
             fixers[name] = Fixer(
                 command, pattern, linerange, priority, metadata, skipclean
             )
     return collections.OrderedDict(
         sorted(fixers.items(), key=lambda item: item[1]._priority, reverse=True)
     )
 
 
 def fixernames(ui):
     """Returns the names of [fix] config options that have suboptions"""
     names = set()
     for k, v in ui.configitems(b'fix'):
         if b':' in k:
             names.add(k.split(b':', 1)[0])
     return names
 
 
 class Fixer(object):
     """Wraps the raw config values for a fixer with methods"""
 
     def __init__(
         self, command, pattern, linerange, priority, metadata, skipclean
     ):
         self._command = command
         self._pattern = pattern
         self._linerange = linerange
         self._priority = priority
         self._metadata = metadata
         self._skipclean = skipclean
 
     def affects(self, opts, fixctx, path):
         """Should this fixer run on the file at the given path and context?"""
         repo = fixctx.repo()
         matcher = matchmod.match(
             repo.root, repo.root, [self._pattern], ctx=fixctx
         )
         return matcher(path)
 
     def shouldoutputmetadata(self):
         """Should the stdout of this fixer start with JSON and a null byte?"""
         return self._metadata
 
     def command(self, ui, path, ranges):
         """A shell command to use to invoke this fixer on the given file/lines
 
         May return None if there is no appropriate command to run for the given
         parameters.
         """
         expand = cmdutil.rendercommandtemplate
         parts = [
             expand(
                 ui,
                 self._command,
                 {b'rootpath': path, b'basename': os.path.basename(path)},
             )
         ]
         if self._linerange:
             if self._skipclean and not ranges:
                 # No line ranges to fix, so don't run the fixer.
                 return None
             for first, last in ranges:
                 parts.append(
                     expand(
                         ui, self._linerange, {b'first': first, b'last': last}
                     )
                 )
         return b' '.join(parts)