histedit: drop fallback to empty string from rendertemplate()

AFAICT, `cmdutil.rendertemplate()` always returns bytes (never
e.g. `None`), so we don't need to fall back to empty
(byte-)string. The fallback has been there since the code was added in
11c076786d56 (histedit: add templating support to histedit's rule file
generation, 2019-01-29).

Differential Revision: https://phab.mercurial-scm.org/D9244

hgext/histedit.py

@@ -1,2639 +1,2633 b''
 # histedit.py - interactive history editing for mercurial
 #
 # Copyright 2009 Augie Fackler <[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.
 """interactive history editing
 
 With this extension installed, Mercurial gains one new command: histedit. Usage
 is as follows, assuming the following history::
 
  @  3[tip]   7c2fd3b9020c   2009-04-27 18:04 -0500   durin42
  |    Add delta
  |
  o  2   030b686bedc4   2009-04-27 18:04 -0500   durin42
  |    Add gamma
  |
  o  1   c561b4e977df   2009-04-27 18:04 -0500   durin42
  |    Add beta
  |
  o  0   d8d2fcd0e319   2009-04-27 18:04 -0500   durin42
       Add alpha
 
 If you were to run ``hg histedit c561b4e977df``, you would see the following
 file open in your editor::
 
  pick c561b4e977df Add beta
  pick 030b686bedc4 Add gamma
  pick 7c2fd3b9020c Add delta
 
  # Edit history between c561b4e977df and 7c2fd3b9020c
  #
  # Commits are listed from least to most recent
  #
  # Commands:
  #  p, pick = use commit
  #  e, edit = use commit, but stop for amending
  #  f, fold = use commit, but combine it with the one above
  #  r, roll = like fold, but discard this commit's description and date
  #  d, drop = remove commit from history
  #  m, mess = edit commit message without changing commit content
  #  b, base = checkout changeset and apply further changesets from there
  #
 
 In this file, lines beginning with ``#`` are ignored. You must specify a rule
 for each revision in your history. For example, if you had meant to add gamma
 before beta, and then wanted to add delta in the same revision as beta, you
 would reorganize the file to look like this::
 
  pick 030b686bedc4 Add gamma
  pick c561b4e977df Add beta
  fold 7c2fd3b9020c Add delta
 
  # Edit history between c561b4e977df and 7c2fd3b9020c
  #
  # Commits are listed from least to most recent
  #
  # Commands:
  #  p, pick = use commit
  #  e, edit = use commit, but stop for amending
  #  f, fold = use commit, but combine it with the one above
  #  r, roll = like fold, but discard this commit's description and date
  #  d, drop = remove commit from history
  #  m, mess = edit commit message without changing commit content
  #  b, base = checkout changeset and apply further changesets from there
  #
 
 At which point you close the editor and ``histedit`` starts working. When you
 specify a ``fold`` operation, ``histedit`` will open an editor when it folds
 those revisions together, offering you a chance to clean up the commit message::
 
  Add beta
  ***
  Add delta
 
 Edit the commit message to your liking, then close the editor. The date used
 for the commit will be the later of the two commits' dates. For this example,
 let's assume that the commit message was changed to ``Add beta and delta.``
 After histedit has run and had a chance to remove any old or temporary
 revisions it needed, the history looks like this::
 
  @  2[tip]   989b4d060121   2009-04-27 18:04 -0500   durin42
  |    Add beta and delta.
  |
  o  1   081603921c3f   2009-04-27 18:04 -0500   durin42
  |    Add gamma
  |
  o  0   d8d2fcd0e319   2009-04-27 18:04 -0500   durin42
       Add alpha
 
 Note that ``histedit`` does *not* remove any revisions (even its own temporary
 ones) until after it has completed all the editing operations, so it will
 probably perform several strip operations when it's done. For the above example,
 it had to run strip twice. Strip can be slow depending on a variety of factors,
 so you might need to be a little patient. You can choose to keep the original
 revisions by passing the ``--keep`` flag.
 
 The ``edit`` operation will drop you back to a command prompt,
 allowing you to edit files freely, or even use ``hg record`` to commit
 some changes as a separate commit. When you're done, any remaining
 uncommitted changes will be committed as well. When done, run ``hg
 histedit --continue`` to finish this step. If there are uncommitted
 changes, you'll be prompted for a new commit message, but the default
 commit message will be the original message for the ``edit`` ed
 revision, and the date of the original commit will be preserved.
 
 The ``message`` operation will give you a chance to revise a commit
 message without changing the contents. It's a shortcut for doing
 ``edit`` immediately followed by `hg histedit --continue``.
 
 If ``histedit`` encounters a conflict when moving a revision (while
 handling ``pick`` or ``fold``), it'll stop in a similar manner to
 ``edit`` with the difference that it won't prompt you for a commit
 message when done. If you decide at this point that you don't like how
 much work it will be to rearrange history, or that you made a mistake,
 you can use ``hg histedit --abort`` to abandon the new changes you
 have made and return to the state before you attempted to edit your
 history.
 
 If we clone the histedit-ed example repository above and add four more
 changes, such that we have the following history::
 
    @  6[tip]   038383181893   2009-04-27 18:04 -0500   stefan
    |    Add theta
    |
    o  5   140988835471   2009-04-27 18:04 -0500   stefan
    |    Add eta
    |
    o  4   122930637314   2009-04-27 18:04 -0500   stefan
    |    Add zeta
    |
    o  3   836302820282   2009-04-27 18:04 -0500   stefan
    |    Add epsilon
    |
    o  2   989b4d060121   2009-04-27 18:04 -0500   durin42
    |    Add beta and delta.
    |
    o  1   081603921c3f   2009-04-27 18:04 -0500   durin42
    |    Add gamma
    |
    o  0   d8d2fcd0e319   2009-04-27 18:04 -0500   durin42
         Add alpha
 
 If you run ``hg histedit --outgoing`` on the clone then it is the same
 as running ``hg histedit 836302820282``. If you need plan to push to a
 repository that Mercurial does not detect to be related to the source
 repo, you can add a ``--force`` option.
 
 Config
 ------
 
 Histedit rule lines are truncated to 80 characters by default. You
 can customize this behavior by setting a different length in your
 configuration file::
 
   [histedit]
   linelen = 120      # truncate rule lines at 120 characters
 
 The summary of a change can be customized as well::
 
   [histedit]
   summary-template = '{rev} {bookmarks} {desc|firstline}'
 
 The customized summary should be kept short enough that rule lines
 will fit in the configured line length. See above if that requires
 customization.
 
 ``hg histedit`` attempts to automatically choose an appropriate base
 revision to use. To change which base revision is used, define a
 revset in your configuration file::
 
   [histedit]
   defaultrev = only(.) & draft()
 
 By default each edited revision needs to be present in histedit commands.
 To remove revision you need to use ``drop`` operation. You can configure
 the drop to be implicit for missing commits by adding::
 
   [histedit]
   dropmissing = True
 
 By default, histedit will close the transaction after each action. For
 performance purposes, you can configure histedit to use a single transaction
 across the entire histedit. WARNING: This setting introduces a significant risk
 of losing the work you've done in a histedit if the histedit aborts
 unexpectedly::
 
   [histedit]
   singletransaction = True
 
 """
 
 from __future__ import absolute_import
 
 # chistedit dependencies that are not available everywhere
 try:
     import fcntl
     import termios
 except ImportError:
     fcntl = None
     termios = None
 
 import functools
 import os
 import struct
 
 from mercurial.i18n import _
 from mercurial.pycompat import (
     getattr,
     open,
 )
 from mercurial import (
     bundle2,
     cmdutil,
     context,
     copies,
     destutil,
     discovery,
     encoding,
     error,
     exchange,
     extensions,
     hg,
     logcmdutil,
     merge as mergemod,
     mergestate as mergestatemod,
     mergeutil,
     node,
     obsolete,
     pycompat,
     registrar,
     repair,
     rewriteutil,
     scmutil,
     state as statemod,
     util,
 )
 from mercurial.utils import (
     dateutil,
     stringutil,
 )
 
 pickle = util.pickle
 cmdtable = {}
 command = registrar.command(cmdtable)
 
 configtable = {}
 configitem = registrar.configitem(configtable)
 configitem(
     b'experimental', b'histedit.autoverb', default=False,
 )
 configitem(
     b'histedit', b'defaultrev', default=None,
 )
 configitem(
     b'histedit', b'dropmissing', default=False,
 )
 configitem(
     b'histedit', b'linelen', default=80,
 )
 configitem(
     b'histedit', b'singletransaction', default=False,
 )
 configitem(
     b'ui', b'interface.histedit', default=None,
 )
 configitem(b'histedit', b'summary-template', default=b'{rev} {desc|firstline}')
 
 # 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'
 
 actiontable = {}
 primaryactions = set()
 secondaryactions = set()
 tertiaryactions = set()
 internalactions = set()
 
 
 def geteditcomment(ui, first, last):
     """ construct the editor comment
     The comment includes::
      - an intro
      - sorted primary commands
      - sorted short commands
      - sorted long commands
      - additional hints
 
     Commands are only included once.
     """
     intro = _(
         b"""Edit history between %s and %s
 
 Commits are listed from least to most recent
 
 You can reorder changesets by reordering the lines
 
 Commands:
 """
     )
     actions = []
 
     def addverb(v):
         a = actiontable[v]
         lines = a.message.split(b"\n")
         if len(a.verbs):
             v = b', '.join(sorted(a.verbs, key=lambda v: len(v)))
         actions.append(b" %s = %s" % (v, lines[0]))
         actions.extend([b'  %s'] * (len(lines) - 1))
 
     for v in (
         sorted(primaryactions)
         + sorted(secondaryactions)
         + sorted(tertiaryactions)
     ):
         addverb(v)
     actions.append(b'')
 
     hints = []
     if ui.configbool(b'histedit', b'dropmissing'):
         hints.append(
             b"Deleting a changeset from the list "
             b"will DISCARD it from the edited history!"
         )
 
     lines = (intro % (first, last)).split(b'\n') + actions + hints
 
     return b''.join([b'# %s\n' % l if l else b'#\n' for l in lines])
 
 
 class histeditstate(object):
     def __init__(self, repo):
         self.repo = repo
         self.actions = None
         self.keep = None
         self.topmost = None
         self.parentctxnode = None
         self.lock = None
         self.wlock = None
         self.backupfile = None
         self.stateobj = statemod.cmdstate(repo, b'histedit-state')
         self.replacements = []
 
     def read(self):
         """Load histedit state from disk and set fields appropriately."""
         if not self.stateobj.exists():
             cmdutil.wrongtooltocontinue(self.repo, _(b'histedit'))
 
         data = self._read()
 
         self.parentctxnode = data[b'parentctxnode']
         actions = parserules(data[b'rules'], self)
         self.actions = actions
         self.keep = data[b'keep']
         self.topmost = data[b'topmost']
         self.replacements = data[b'replacements']
         self.backupfile = data[b'backupfile']
 
     def _read(self):
         fp = self.repo.vfs.read(b'histedit-state')
         if fp.startswith(b'v1\n'):
             data = self._load()
             parentctxnode, rules, keep, topmost, replacements, backupfile = data
         else:
             data = pickle.loads(fp)
             parentctxnode, rules, keep, topmost, replacements = data
             backupfile = None
         rules = b"\n".join([b"%s %s" % (verb, rest) for [verb, rest] in rules])
 
         return {
             b'parentctxnode': parentctxnode,
             b"rules": rules,
             b"keep": keep,
             b"topmost": topmost,
             b"replacements": replacements,
             b"backupfile": backupfile,
         }
 
     def write(self, tr=None):
         if tr:
             tr.addfilegenerator(
                 b'histedit-state',
                 (b'histedit-state',),
                 self._write,
                 location=b'plain',
             )
         else:
             with self.repo.vfs(b"histedit-state", b"w") as f:
                 self._write(f)
 
     def _write(self, fp):
         fp.write(b'v1\n')
         fp.write(b'%s\n' % node.hex(self.parentctxnode))
         fp.write(b'%s\n' % node.hex(self.topmost))
         fp.write(b'%s\n' % (b'True' if self.keep else b'False'))
         fp.write(b'%d\n' % len(self.actions))
         for action in self.actions:
             fp.write(b'%s\n' % action.tostate())
         fp.write(b'%d\n' % len(self.replacements))
         for replacement in self.replacements:
             fp.write(
                 b'%s%s\n'
                 % (
                     node.hex(replacement[0]),
                     b''.join(node.hex(r) for r in replacement[1]),
                 )
             )
         backupfile = self.backupfile
         if not backupfile:
             backupfile = b''
         fp.write(b'%s\n' % backupfile)
 
     def _load(self):
         fp = self.repo.vfs(b'histedit-state', b'r')
         lines = [l[:-1] for l in fp.readlines()]
 
         index = 0
         lines[index]  # version number
         index += 1
 
         parentctxnode = node.bin(lines[index])
         index += 1
 
         topmost = node.bin(lines[index])
         index += 1
 
         keep = lines[index] == b'True'
         index += 1
 
         # Rules
         rules = []
         rulelen = int(lines[index])
         index += 1
         for i in pycompat.xrange(rulelen):
             ruleaction = lines[index]
             index += 1
             rule = lines[index]
             index += 1
             rules.append((ruleaction, rule))
 
         # Replacements
         replacements = []
         replacementlen = int(lines[index])
         index += 1
         for i in pycompat.xrange(replacementlen):
             replacement = lines[index]
             original = node.bin(replacement[:40])
             succ = [
                 node.bin(replacement[i : i + 40])
                 for i in range(40, len(replacement), 40)
             ]
             replacements.append((original, succ))
             index += 1
 
         backupfile = lines[index]
         index += 1
 
         fp.close()
 
         return parentctxnode, rules, keep, topmost, replacements, backupfile
 
     def clear(self):
         if self.inprogress():
             self.repo.vfs.unlink(b'histedit-state')
 
     def inprogress(self):
         return self.repo.vfs.exists(b'histedit-state')
 
 
 class histeditaction(object):
     def __init__(self, state, node):
         self.state = state
         self.repo = state.repo
         self.node = node
 
     @classmethod
     def fromrule(cls, state, rule):
         """Parses the given rule, returning an instance of the histeditaction.
         """
         ruleid = rule.strip().split(b' ', 1)[0]
         # ruleid can be anything from rev numbers, hashes, "bookmarks" etc
         # Check for validation of rule ids and get the rulehash
         try:
             rev = node.bin(ruleid)
         except TypeError:
             try:
                 _ctx = scmutil.revsingle(state.repo, ruleid)
                 rulehash = _ctx.hex()
                 rev = node.bin(rulehash)
             except error.RepoLookupError:
                 raise error.ParseError(_(b"invalid changeset %s") % ruleid)
         return cls(state, rev)
 
     def verify(self, prev, expected, seen):
         """ Verifies semantic correctness of the rule"""
         repo = self.repo
         ha = node.hex(self.node)
         self.node = scmutil.resolvehexnodeidprefix(repo, ha)
         if self.node is None:
             raise error.ParseError(_(b'unknown changeset %s listed') % ha[:12])
         self._verifynodeconstraints(prev, expected, seen)
 
     def _verifynodeconstraints(self, prev, expected, seen):
         # by default command need a node in the edited list
         if self.node not in expected:
             raise error.ParseError(
                 _(b'%s "%s" changeset was not a candidate')
                 % (self.verb, node.short(self.node)),
                 hint=_(b'only use listed changesets'),
             )
         # and only one command per node
         if self.node in seen:
             raise error.ParseError(
                 _(b'duplicated command for changeset %s')
                 % node.short(self.node)
             )
 
     def torule(self):
         """build a histedit rule line for an action
 
         by default lines are in the form:
         <hash> <rev> <summary>
         """
         ctx = self.repo[self.node]
         ui = self.repo.ui
-        summary = (
-            cmdutil.rendertemplate(
+        summary = cmdutil.rendertemplate(
                 ctx, ui.config(b'histedit', b'summary-template')
             )
-            or b''
-        )
         summary = summary.splitlines()[0]
         line = b'%s %s %s' % (self.verb, ctx, summary)
         # trim to 75 columns by default so it's not stupidly wide in my editor
         # (the 5 more are left for verb)
         maxlen = self.repo.ui.configint(b'histedit', b'linelen')
         maxlen = max(maxlen, 22)  # avoid truncating hash
         return stringutil.ellipsis(line, maxlen)
 
     def tostate(self):
         """Print an action in format used by histedit state files
            (the first line is a verb, the remainder is the second)
         """
         return b"%s\n%s" % (self.verb, node.hex(self.node))
 
     def run(self):
         """Runs the action. The default behavior is simply apply the action's
         rulectx onto the current parentctx."""
         self.applychange()
         self.continuedirty()
         return self.continueclean()
 
     def applychange(self):
         """Applies the changes from this action's rulectx onto the current
         parentctx, but does not commit them."""
         repo = self.repo
         rulectx = repo[self.node]
         repo.ui.pushbuffer(error=True, labeled=True)
         hg.update(repo, self.state.parentctxnode, quietempty=True)
         repo.ui.popbuffer()
         stats = applychanges(repo.ui, repo, rulectx, {})
         repo.dirstate.setbranch(rulectx.branch())
         if stats.unresolvedcount:
             raise error.InterventionRequired(
                 _(b'Fix up the change (%s %s)')
                 % (self.verb, node.short(self.node)),
                 hint=_(b'hg histedit --continue to resume'),
             )
 
     def continuedirty(self):
         """Continues the action when changes have been applied to the working
         copy. The default behavior is to commit the dirty changes."""
         repo = self.repo
         rulectx = repo[self.node]
 
         editor = self.commiteditor()
         commit = commitfuncfor(repo, rulectx)
         if repo.ui.configbool(b'rewrite', b'update-timestamp'):
             date = dateutil.makedate()
         else:
             date = rulectx.date()
         commit(
             text=rulectx.description(),
             user=rulectx.user(),
             date=date,
             extra=rulectx.extra(),
             editor=editor,
         )
 
     def commiteditor(self):
         """The editor to be used to edit the commit message."""
         return False
 
     def continueclean(self):
         """Continues the action when the working copy is clean. The default
         behavior is to accept the current commit as the new version of the
         rulectx."""
         ctx = self.repo[b'.']
         if ctx.node() == self.state.parentctxnode:
             self.repo.ui.warn(
                 _(b'%s: skipping changeset (no changes)\n')
                 % node.short(self.node)
             )
             return ctx, [(self.node, tuple())]
         if ctx.node() == self.node:
             # Nothing changed
             return ctx, []
         return ctx, [(self.node, (ctx.node(),))]
 
 
 def commitfuncfor(repo, src):
     """Build a commit function for the replacement of <src>
 
     This function ensure we apply the same treatment to all changesets.
 
     - Add a 'histedit_source' entry in extra.
 
     Note that fold has its own separated logic because its handling is a bit
     different and not easily factored out of the fold method.
     """
     phasemin = src.phase()
 
     def commitfunc(**kwargs):
         overrides = {(b'phases', b'new-commit'): phasemin}
         with repo.ui.configoverride(overrides, b'histedit'):
             extra = kwargs.get('extra', {}).copy()
             extra[b'histedit_source'] = src.hex()
             kwargs['extra'] = extra
             return repo.commit(**kwargs)
 
     return commitfunc
 
 
 def applychanges(ui, repo, ctx, opts):
     """Merge changeset from ctx (only) in the current working directory"""
     if ctx.p1().node() == repo.dirstate.p1():
         # edits are "in place" we do not need to make any merge,
         # just applies changes on parent for editing
         ui.pushbuffer()
         cmdutil.revert(ui, repo, ctx, all=True)
         stats = mergemod.updateresult(0, 0, 0, 0)
         ui.popbuffer()
     else:
         try:
             # ui.forcemerge is an internal variable, do not document
             repo.ui.setconfig(
                 b'ui', b'forcemerge', opts.get(b'tool', b''), b'histedit'
             )
             stats = mergemod.graft(repo, ctx, labels=[b'local', b'histedit'])
         finally:
             repo.ui.setconfig(b'ui', b'forcemerge', b'', b'histedit')
     return stats
 
 
 def collapse(repo, firstctx, lastctx, commitopts, skipprompt=False):
     """collapse the set of revisions from first to last as new one.
 
     Expected commit options are:
         - message
         - date
         - username
     Commit message is edited in all cases.
 
     This function works in memory."""
     ctxs = list(repo.set(b'%d::%d', firstctx.rev(), lastctx.rev()))
     if not ctxs:
         return None
     for c in ctxs:
         if not c.mutable():
             raise error.ParseError(
                 _(b"cannot fold into public change %s") % node.short(c.node())
             )
     base = firstctx.p1()
 
     # commit a new version of the old changeset, including the update
     # collect all files which might be affected
     files = set()
     for ctx in ctxs:
         files.update(ctx.files())
 
     # Recompute copies (avoid recording a -> b -> a)
     copied = copies.pathcopies(base, lastctx)
 
     # prune files which were reverted by the updates
     files = [f for f in files if not cmdutil.samefile(f, lastctx, base)]
     # commit version of these files as defined by head
     headmf = lastctx.manifest()
 
     def filectxfn(repo, ctx, path):
         if path in headmf:
             fctx = lastctx[path]
             flags = fctx.flags()
             mctx = context.memfilectx(
                 repo,
                 ctx,
                 fctx.path(),
                 fctx.data(),
                 islink=b'l' in flags,
                 isexec=b'x' in flags,
                 copysource=copied.get(path),
             )
             return mctx
         return None
 
     if commitopts.get(b'message'):
         message = commitopts[b'message']
     else:
         message = firstctx.description()
     user = commitopts.get(b'user')
     date = commitopts.get(b'date')
     extra = commitopts.get(b'extra')
 
     parents = (firstctx.p1().node(), firstctx.p2().node())
     editor = None
     if not skipprompt:
         editor = cmdutil.getcommiteditor(edit=True, editform=b'histedit.fold')
     new = context.memctx(
         repo,
         parents=parents,
         text=message,
         files=files,
         filectxfn=filectxfn,
         user=user,
         date=date,
         extra=extra,
         editor=editor,
     )
     return repo.commitctx(new)
 
 
 def _isdirtywc(repo):
     return repo[None].dirty(missing=True)
 
 
 def abortdirty():
     raise error.Abort(
         _(b'working copy has pending changes'),
         hint=_(
             b'amend, commit, or revert them and run histedit '
             b'--continue, or abort with histedit --abort'
         ),
     )
 
 
 def action(verbs, message, priority=False, internal=False):
     def wrap(cls):
         assert not priority or not internal
         verb = verbs[0]
         if priority:
             primaryactions.add(verb)
         elif internal:
             internalactions.add(verb)
         elif len(verbs) > 1:
             secondaryactions.add(verb)
         else:
             tertiaryactions.add(verb)
 
         cls.verb = verb
         cls.verbs = verbs
         cls.message = message
         for verb in verbs:
             actiontable[verb] = cls
         return cls
 
     return wrap
 
 
 @action([b'pick', b'p'], _(b'use commit'), priority=True)
 class pick(histeditaction):
     def run(self):
         rulectx = self.repo[self.node]
         if rulectx.p1().node() == self.state.parentctxnode:
             self.repo.ui.debug(b'node %s unchanged\n' % node.short(self.node))
             return rulectx, []
 
         return super(pick, self).run()
 
 
 @action([b'edit', b'e'], _(b'use commit, but stop for amending'), priority=True)
 class edit(histeditaction):
     def run(self):
         repo = self.repo
         rulectx = repo[self.node]
         hg.update(repo, self.state.parentctxnode, quietempty=True)
         applychanges(repo.ui, repo, rulectx, {})
         raise error.InterventionRequired(
             _(b'Editing (%s), you may commit or record as needed now.')
             % node.short(self.node),
             hint=_(b'hg histedit --continue to resume'),
         )
 
     def commiteditor(self):
         return cmdutil.getcommiteditor(edit=True, editform=b'histedit.edit')
 
 
 @action([b'fold', b'f'], _(b'use commit, but combine it with the one above'))
 class fold(histeditaction):
     def verify(self, prev, expected, seen):
         """ Verifies semantic correctness of the fold rule"""
         super(fold, self).verify(prev, expected, seen)
         repo = self.repo
         if not prev:
             c = repo[self.node].p1()
         elif not prev.verb in (b'pick', b'base'):
             return
         else:
             c = repo[prev.node]
         if not c.mutable():
             raise error.ParseError(
                 _(b"cannot fold into public change %s") % node.short(c.node())
             )
 
     def continuedirty(self):
         repo = self.repo
         rulectx = repo[self.node]
 
         commit = commitfuncfor(repo, rulectx)
         commit(
             text=b'fold-temp-revision %s' % node.short(self.node),
             user=rulectx.user(),
             date=rulectx.date(),
             extra=rulectx.extra(),
         )
 
     def continueclean(self):
         repo = self.repo
         ctx = repo[b'.']
         rulectx = repo[self.node]
         parentctxnode = self.state.parentctxnode
         if ctx.node() == parentctxnode:
             repo.ui.warn(_(b'%s: empty changeset\n') % node.short(self.node))
             return ctx, [(self.node, (parentctxnode,))]
 
         parentctx = repo[parentctxnode]
         newcommits = {
             c.node()
             for c in repo.set(b'(%d::. - %d)', parentctx.rev(), parentctx.rev())
         }
         if not newcommits:
             repo.ui.warn(
                 _(
                     b'%s: cannot fold - working copy is not a '
                     b'descendant of previous commit %s\n'
                 )
                 % (node.short(self.node), node.short(parentctxnode))
             )
             return ctx, [(self.node, (ctx.node(),))]
 
         middlecommits = newcommits.copy()
         middlecommits.discard(ctx.node())
 
         return self.finishfold(
             repo.ui, repo, parentctx, rulectx, ctx.node(), middlecommits
         )
 
     def skipprompt(self):
         """Returns true if the rule should skip the message editor.
 
         For example, 'fold' wants to show an editor, but 'rollup'
         doesn't want to.
         """
         return False
 
     def mergedescs(self):
         """Returns true if the rule should merge messages of multiple changes.
 
         This exists mainly so that 'rollup' rules can be a subclass of
         'fold'.
         """
         return True
 
     def firstdate(self):
         """Returns true if the rule should preserve the date of the first
         change.
 
         This exists mainly so that 'rollup' rules can be a subclass of
         'fold'.
         """
         return False
 
     def finishfold(self, ui, repo, ctx, oldctx, newnode, internalchanges):
         mergemod.update(ctx.p1())
         ### prepare new commit data
         commitopts = {}
         commitopts[b'user'] = ctx.user()
         # commit message
         if not self.mergedescs():
             newmessage = ctx.description()
         else:
             newmessage = (
                 b'\n***\n'.join(
                     [ctx.description()]
                     + [repo[r].description() for r in internalchanges]
                     + [oldctx.description()]
                 )
                 + b'\n'
             )
         commitopts[b'message'] = newmessage
         # date
         if self.firstdate():
             commitopts[b'date'] = ctx.date()
         else:
             commitopts[b'date'] = max(ctx.date(), oldctx.date())
         # if date is to be updated to current
         if ui.configbool(b'rewrite', b'update-timestamp'):
             commitopts[b'date'] = dateutil.makedate()
 
         extra = ctx.extra().copy()
         # histedit_source
         # note: ctx is likely a temporary commit but that the best we can do
         #       here. This is sufficient to solve issue3681 anyway.
         extra[b'histedit_source'] = b'%s,%s' % (ctx.hex(), oldctx.hex())
         commitopts[b'extra'] = extra
         phasemin = max(ctx.phase(), oldctx.phase())
         overrides = {(b'phases', b'new-commit'): phasemin}
         with repo.ui.configoverride(overrides, b'histedit'):
             n = collapse(
                 repo,
                 ctx,
                 repo[newnode],
                 commitopts,
                 skipprompt=self.skipprompt(),
             )
         if n is None:
             return ctx, []
         mergemod.update(repo[n])
         replacements = [
             (oldctx.node(), (newnode,)),
             (ctx.node(), (n,)),
             (newnode, (n,)),
         ]
         for ich in internalchanges:
             replacements.append((ich, (n,)))
         return repo[n], replacements
 
 
 @action(
     [b'base', b'b'],
     _(b'checkout changeset and apply further changesets from there'),
 )
 class base(histeditaction):
     def run(self):
         if self.repo[b'.'].node() != self.node:
             mergemod.clean_update(self.repo[self.node])
         return self.continueclean()
 
     def continuedirty(self):
         abortdirty()
 
     def continueclean(self):
         basectx = self.repo[b'.']
         return basectx, []
 
     def _verifynodeconstraints(self, prev, expected, seen):
         # base can only be use with a node not in the edited set
         if self.node in expected:
             msg = _(b'%s "%s" changeset was an edited list candidate')
             raise error.ParseError(
                 msg % (self.verb, node.short(self.node)),
                 hint=_(b'base must only use unlisted changesets'),
             )
 
 
 @action(
     [b'_multifold'],
     _(
         """fold subclass used for when multiple folds happen in a row
 
     We only want to fire the editor for the folded message once when
     (say) four changes are folded down into a single change. This is
     similar to rollup, but we should preserve both messages so that
     when the last fold operation runs we can show the user all the
     commit messages in their editor.
     """
     ),
     internal=True,
 )
 class _multifold(fold):
     def skipprompt(self):
         return True
 
 
 @action(
     [b"roll", b"r"],
     _(b"like fold, but discard this commit's description and date"),
 )
 class rollup(fold):
     def mergedescs(self):
         return False
 
     def skipprompt(self):
         return True
 
     def firstdate(self):
         return True
 
 
 @action([b"drop", b"d"], _(b'remove commit from history'))
 class drop(histeditaction):
     def run(self):
         parentctx = self.repo[self.state.parentctxnode]
         return parentctx, [(self.node, tuple())]
 
 
 @action(
     [b"mess", b"m"],
     _(b'edit commit message without changing commit content'),
     priority=True,
 )
 class message(histeditaction):
     def commiteditor(self):
         return cmdutil.getcommiteditor(edit=True, editform=b'histedit.mess')
 
 
 def findoutgoing(ui, repo, remote=None, force=False, opts=None):
     """utility function to find the first outgoing changeset
 
     Used by initialization code"""
     if opts is None:
         opts = {}
     dest = ui.expandpath(remote or b'default-push', remote or b'default')
     dest, branches = hg.parseurl(dest, None)[:2]
     ui.status(_(b'comparing with %s\n') % util.hidepassword(dest))
 
     revs, checkout = hg.addbranchrevs(repo, repo, branches, None)
     other = hg.peer(repo, opts, dest)
 
     if revs:
         revs = [repo.lookup(rev) for rev in revs]
 
     outgoing = discovery.findcommonoutgoing(repo, other, revs, force=force)
     if not outgoing.missing:
         raise error.Abort(_(b'no outgoing ancestors'))
     roots = list(repo.revs(b"roots(%ln)", outgoing.missing))
     if len(roots) > 1:
         msg = _(b'there are ambiguous outgoing revisions')
         hint = _(b"see 'hg help histedit' for more detail")
         raise error.Abort(msg, hint=hint)
     return repo[roots[0]].node()
 
 
 # Curses Support
 try:
     import curses
 except ImportError:
     curses = None
 
 KEY_LIST = [b'pick', b'edit', b'fold', b'drop', b'mess', b'roll']
 ACTION_LABELS = {
     b'fold': b'^fold',
     b'roll': b'^roll',
 }
 
 COLOR_HELP, COLOR_SELECTED, COLOR_OK, COLOR_WARN, COLOR_CURRENT = 1, 2, 3, 4, 5
 COLOR_DIFF_ADD_LINE, COLOR_DIFF_DEL_LINE, COLOR_DIFF_OFFSET = 6, 7, 8
 COLOR_ROLL, COLOR_ROLL_CURRENT, COLOR_ROLL_SELECTED = 9, 10, 11
 
 E_QUIT, E_HISTEDIT = 1, 2
 E_PAGEDOWN, E_PAGEUP, E_LINEUP, E_LINEDOWN, E_RESIZE = 3, 4, 5, 6, 7
 MODE_INIT, MODE_PATCH, MODE_RULES, MODE_HELP = 0, 1, 2, 3
 
 KEYTABLE = {
     b'global': {
         b'h': b'next-action',
         b'KEY_RIGHT': b'next-action',
         b'l': b'prev-action',
         b'KEY_LEFT': b'prev-action',
         b'q': b'quit',
         b'c': b'histedit',
         b'C': b'histedit',
         b'v': b'showpatch',
         b'?': b'help',
     },
     MODE_RULES: {
         b'd': b'action-drop',
         b'e': b'action-edit',
         b'f': b'action-fold',
         b'm': b'action-mess',
         b'p': b'action-pick',
         b'r': b'action-roll',
         b' ': b'select',
         b'j': b'down',
         b'k': b'up',
         b'KEY_DOWN': b'down',
         b'KEY_UP': b'up',
         b'J': b'move-down',
         b'K': b'move-up',
         b'KEY_NPAGE': b'move-down',
         b'KEY_PPAGE': b'move-up',
         b'0': b'goto',  # Used for 0..9
     },
     MODE_PATCH: {
         b' ': b'page-down',
         b'KEY_NPAGE': b'page-down',
         b'KEY_PPAGE': b'page-up',
         b'j': b'line-down',
         b'k': b'line-up',
         b'KEY_DOWN': b'line-down',
         b'KEY_UP': b'line-up',
         b'J': b'down',
         b'K': b'up',
     },
     MODE_HELP: {},
 }
 
 
 def screen_size():
     return struct.unpack(b'hh', fcntl.ioctl(1, termios.TIOCGWINSZ, b'    '))
 
 
 class histeditrule(object):
     def __init__(self, ui, ctx, pos, action=b'pick'):
         self.ui = ui
         self.ctx = ctx
         self.action = action
         self.origpos = pos
         self.pos = pos
         self.conflicts = []
 
     def __bytes__(self):
         # Example display of several histeditrules:
         #
         #  #10 pick   316392:06a16c25c053   add option to skip tests
         #  #11 ^roll  316393:71313c964cc5   <RED>oops a fixup commit</RED>
         #  #12 pick   316394:ab31f3973b0d   include mfbt for mozilla-config.h
         #  #13 ^fold  316395:14ce5803f4c3   fix warnings
         #
         # The carets point to the changeset being folded into ("roll this
         # changeset into the changeset above").
         return b'%s%s' % (self.prefix, self.desc)
 
     __str__ = encoding.strmethod(__bytes__)
 
     @property
     def prefix(self):
         # Some actions ('fold' and 'roll') combine a patch with a
         # previous one. Add a marker showing which patch they apply
         # to.
         action = ACTION_LABELS.get(self.action, self.action)
 
         h = self.ctx.hex()[0:12]
         r = self.ctx.rev()
 
         return b"#%s %s %d:%s   " % (
             (b'%d' % self.origpos).ljust(2),
             action.ljust(6),
             r,
             h,
         )
 
     @util.propertycache
     def desc(self):
-        summary = (
-            cmdutil.rendertemplate(
+        summary = cmdutil.rendertemplate(
                 self.ctx, self.ui.config(b'histedit', b'summary-template')
             )
-            or b''
-        )
         if summary:
             return summary
         # This is split off from the prefix property so that we can
         # separately make the description for 'roll' red (since it
         # will get discarded).
         return self.ctx.description().splitlines()[0].strip()
 
     def checkconflicts(self, other):
         if other.pos > self.pos and other.origpos <= self.origpos:
             if set(other.ctx.files()) & set(self.ctx.files()) != set():
                 self.conflicts.append(other)
                 return self.conflicts
 
         if other in self.conflicts:
             self.conflicts.remove(other)
         return self.conflicts
 
 
 # ============ EVENTS ===============
 def movecursor(state, oldpos, newpos):
     '''Change the rule/changeset that the cursor is pointing to, regardless of
     current mode (you can switch between patches from the view patch window).'''
     state[b'pos'] = newpos
 
     mode, _ = state[b'mode']
     if mode == MODE_RULES:
         # Scroll through the list by updating the view for MODE_RULES, so that
         # even if we are not currently viewing the rules, switching back will
         # result in the cursor's rule being visible.
         modestate = state[b'modes'][MODE_RULES]
         if newpos < modestate[b'line_offset']:
             modestate[b'line_offset'] = newpos
         elif newpos > modestate[b'line_offset'] + state[b'page_height'] - 1:
             modestate[b'line_offset'] = newpos - state[b'page_height'] + 1
 
     # Reset the patch view region to the top of the new patch.
     state[b'modes'][MODE_PATCH][b'line_offset'] = 0
 
 
 def changemode(state, mode):
     curmode, _ = state[b'mode']
     state[b'mode'] = (mode, curmode)
     if mode == MODE_PATCH:
         state[b'modes'][MODE_PATCH][b'patchcontents'] = patchcontents(state)
 
 
 def makeselection(state, pos):
     state[b'selected'] = pos
 
 
 def swap(state, oldpos, newpos):
     """Swap two positions and calculate necessary conflicts in
     O(|newpos-oldpos|) time"""
 
     rules = state[b'rules']
     assert 0 <= oldpos < len(rules) and 0 <= newpos < len(rules)
 
     rules[oldpos], rules[newpos] = rules[newpos], rules[oldpos]
 
     # TODO: swap should not know about histeditrule's internals
     rules[newpos].pos = newpos
     rules[oldpos].pos = oldpos
 
     start = min(oldpos, newpos)
     end = max(oldpos, newpos)
     for r in pycompat.xrange(start, end + 1):
         rules[newpos].checkconflicts(rules[r])
         rules[oldpos].checkconflicts(rules[r])
 
     if state[b'selected']:
         makeselection(state, newpos)
 
 
 def changeaction(state, pos, action):
     """Change the action state on the given position to the new action"""
     rules = state[b'rules']
     assert 0 <= pos < len(rules)
     rules[pos].action = action
 
 
 def cycleaction(state, pos, next=False):
     """Changes the action state the next or the previous action from
     the action list"""
     rules = state[b'rules']
     assert 0 <= pos < len(rules)
     current = rules[pos].action
 
     assert current in KEY_LIST
 
     index = KEY_LIST.index(current)
     if next:
         index += 1
     else:
         index -= 1
     changeaction(state, pos, KEY_LIST[index % len(KEY_LIST)])
 
 
 def changeview(state, delta, unit):
     '''Change the region of whatever is being viewed (a patch or the list of
     changesets). 'delta' is an amount (+/- 1) and 'unit' is 'page' or 'line'.'''
     mode, _ = state[b'mode']
     if mode != MODE_PATCH:
         return
     mode_state = state[b'modes'][mode]
     num_lines = len(mode_state[b'patchcontents'])
     page_height = state[b'page_height']
     unit = page_height if unit == b'page' else 1
     num_pages = 1 + (num_lines - 1) // page_height
     max_offset = (num_pages - 1) * page_height
     newline = mode_state[b'line_offset'] + delta * unit
     mode_state[b'line_offset'] = max(0, min(max_offset, newline))
 
 
 def event(state, ch):
     """Change state based on the current character input
 
     This takes the current state and based on the current character input from
     the user we change the state.
     """
     selected = state[b'selected']
     oldpos = state[b'pos']
     rules = state[b'rules']
 
     if ch in (curses.KEY_RESIZE, b"KEY_RESIZE"):
         return E_RESIZE
 
     lookup_ch = ch
     if ch is not None and b'0' <= ch <= b'9':
         lookup_ch = b'0'
 
     curmode, prevmode = state[b'mode']
     action = KEYTABLE[curmode].get(
         lookup_ch, KEYTABLE[b'global'].get(lookup_ch)
     )
     if action is None:
         return
     if action in (b'down', b'move-down'):
         newpos = min(oldpos + 1, len(rules) - 1)
         movecursor(state, oldpos, newpos)
         if selected is not None or action == b'move-down':
             swap(state, oldpos, newpos)
     elif action in (b'up', b'move-up'):
         newpos = max(0, oldpos - 1)
         movecursor(state, oldpos, newpos)
         if selected is not None or action == b'move-up':
             swap(state, oldpos, newpos)
     elif action == b'next-action':
         cycleaction(state, oldpos, next=True)
     elif action == b'prev-action':
         cycleaction(state, oldpos, next=False)
     elif action == b'select':
         selected = oldpos if selected is None else None
         makeselection(state, selected)
     elif action == b'goto' and int(ch) < len(rules) and len(rules) <= 10:
         newrule = next((r for r in rules if r.origpos == int(ch)))
         movecursor(state, oldpos, newrule.pos)
         if selected is not None:
             swap(state, oldpos, newrule.pos)
     elif action.startswith(b'action-'):
         changeaction(state, oldpos, action[7:])
     elif action == b'showpatch':
         changemode(state, MODE_PATCH if curmode != MODE_PATCH else prevmode)
     elif action == b'help':
         changemode(state, MODE_HELP if curmode != MODE_HELP else prevmode)
     elif action == b'quit':
         return E_QUIT
     elif action == b'histedit':
         return E_HISTEDIT
     elif action == b'page-down':
         return E_PAGEDOWN
     elif action == b'page-up':
         return E_PAGEUP
     elif action == b'line-down':
         return E_LINEDOWN
     elif action == b'line-up':
         return E_LINEUP
 
 
 def makecommands(rules):
     """Returns a list of commands consumable by histedit --commands based on
     our list of rules"""
     commands = []
     for rules in rules:
         commands.append(b'%s %s\n' % (rules.action, rules.ctx))
     return commands
 
 
 def addln(win, y, x, line, color=None):
     """Add a line to the given window left padding but 100% filled with
     whitespace characters, so that the color appears on the whole line"""
     maxy, maxx = win.getmaxyx()
     length = maxx - 1 - x
     line = bytes(line).ljust(length)[:length]
     if y < 0:
         y = maxy + y
     if x < 0:
         x = maxx + x
     if color:
         win.addstr(y, x, line, color)
     else:
         win.addstr(y, x, line)
 
 
 def _trunc_head(line, n):
     if len(line) <= n:
         return line
     return b'> ' + line[-(n - 2) :]
 
 
 def _trunc_tail(line, n):
     if len(line) <= n:
         return line
     return line[: n - 2] + b' >'
 
 
 def patchcontents(state):
     repo = state[b'repo']
     rule = state[b'rules'][state[b'pos']]
     displayer = logcmdutil.changesetdisplayer(
         repo.ui, repo, {b"patch": True, b"template": b"status"}, buffered=True
     )
     overrides = {(b'ui', b'verbose'): True}
     with repo.ui.configoverride(overrides, source=b'histedit'):
         displayer.show(rule.ctx)
         displayer.close()
     return displayer.hunk[rule.ctx.rev()].splitlines()
 
 
 def _chisteditmain(repo, rules, stdscr):
     try:
         curses.use_default_colors()
     except curses.error:
         pass
 
     # initialize color pattern
     curses.init_pair(COLOR_HELP, curses.COLOR_WHITE, curses.COLOR_BLUE)
     curses.init_pair(COLOR_SELECTED, curses.COLOR_BLACK, curses.COLOR_WHITE)
     curses.init_pair(COLOR_WARN, curses.COLOR_BLACK, curses.COLOR_YELLOW)
     curses.init_pair(COLOR_OK, curses.COLOR_BLACK, curses.COLOR_GREEN)
     curses.init_pair(COLOR_CURRENT, curses.COLOR_WHITE, curses.COLOR_MAGENTA)
     curses.init_pair(COLOR_DIFF_ADD_LINE, curses.COLOR_GREEN, -1)
     curses.init_pair(COLOR_DIFF_DEL_LINE, curses.COLOR_RED, -1)
     curses.init_pair(COLOR_DIFF_OFFSET, curses.COLOR_MAGENTA, -1)
     curses.init_pair(COLOR_ROLL, curses.COLOR_RED, -1)
     curses.init_pair(
         COLOR_ROLL_CURRENT, curses.COLOR_BLACK, curses.COLOR_MAGENTA
     )
     curses.init_pair(COLOR_ROLL_SELECTED, curses.COLOR_RED, curses.COLOR_WHITE)
 
     # don't display the cursor
     try:
         curses.curs_set(0)
     except curses.error:
         pass
 
     def rendercommit(win, state):
         """Renders the commit window that shows the log of the current selected
         commit"""
         pos = state[b'pos']
         rules = state[b'rules']
         rule = rules[pos]
 
         ctx = rule.ctx
         win.box()
 
         maxy, maxx = win.getmaxyx()
         length = maxx - 3
 
         line = b"changeset: %d:%s" % (ctx.rev(), ctx.hex()[:12])
         win.addstr(1, 1, line[:length])
 
         line = b"user:      %s" % ctx.user()
         win.addstr(2, 1, line[:length])
 
         bms = repo.nodebookmarks(ctx.node())
         line = b"bookmark:  %s" % b' '.join(bms)
         win.addstr(3, 1, line[:length])
 
         line = b"summary:   %s" % (ctx.description().splitlines()[0])
         win.addstr(4, 1, line[:length])
 
         line = b"files:     "
         win.addstr(5, 1, line)
         fnx = 1 + len(line)
         fnmaxx = length - fnx + 1
         y = 5
         fnmaxn = maxy - (1 + y) - 1
         files = ctx.files()
         for i, line1 in enumerate(files):
             if len(files) > fnmaxn and i == fnmaxn - 1:
                 win.addstr(y, fnx, _trunc_tail(b','.join(files[i:]), fnmaxx))
                 y = y + 1
                 break
             win.addstr(y, fnx, _trunc_head(line1, fnmaxx))
             y = y + 1
 
         conflicts = rule.conflicts
         if len(conflicts) > 0:
             conflictstr = b','.join(map(lambda r: r.ctx.hex()[:12], conflicts))
             conflictstr = b"changed files overlap with %s" % conflictstr
         else:
             conflictstr = b'no overlap'
 
         win.addstr(y, 1, conflictstr[:length])
         win.noutrefresh()
 
     def helplines(mode):
         if mode == MODE_PATCH:
             help = b"""\
 ?: help, k/up: line up, j/down: line down, v: stop viewing patch
 pgup: prev page, space/pgdn: next page, c: commit, q: abort
 """
         else:
             help = b"""\
 ?: help, k/up: move up, j/down: move down, space: select, v: view patch
 d: drop, e: edit, f: fold, m: mess, p: pick, r: roll
 pgup/K: move patch up, pgdn/J: move patch down, c: commit, q: abort
 """
         return help.splitlines()
 
     def renderhelp(win, state):
         maxy, maxx = win.getmaxyx()
         mode, _ = state[b'mode']
         for y, line in enumerate(helplines(mode)):
             if y >= maxy:
                 break
             addln(win, y, 0, line, curses.color_pair(COLOR_HELP))
         win.noutrefresh()
 
     def renderrules(rulesscr, state):
         rules = state[b'rules']
         pos = state[b'pos']
         selected = state[b'selected']
         start = state[b'modes'][MODE_RULES][b'line_offset']
 
         conflicts = [r.ctx for r in rules if r.conflicts]
         if len(conflicts) > 0:
             line = b"potential conflict in %s" % b','.join(
                 map(pycompat.bytestr, conflicts)
             )
             addln(rulesscr, -1, 0, line, curses.color_pair(COLOR_WARN))
 
         for y, rule in enumerate(rules[start:]):
             if y >= state[b'page_height']:
                 break
             if len(rule.conflicts) > 0:
                 rulesscr.addstr(y, 0, b" ", curses.color_pair(COLOR_WARN))
             else:
                 rulesscr.addstr(y, 0, b" ", curses.COLOR_BLACK)
 
             if y + start == selected:
                 rollcolor = COLOR_ROLL_SELECTED
                 addln(rulesscr, y, 2, rule, curses.color_pair(COLOR_SELECTED))
             elif y + start == pos:
                 rollcolor = COLOR_ROLL_CURRENT
                 addln(
                     rulesscr,
                     y,
                     2,
                     rule,
                     curses.color_pair(COLOR_CURRENT) | curses.A_BOLD,
                 )
             else:
                 rollcolor = COLOR_ROLL
                 addln(rulesscr, y, 2, rule)
 
             if rule.action == b'roll':
                 rulesscr.addstr(
                     y,
                     2 + len(rule.prefix),
                     rule.desc,
                     curses.color_pair(rollcolor),
                 )
 
         rulesscr.noutrefresh()
 
     def renderstring(win, state, output, diffcolors=False):
         maxy, maxx = win.getmaxyx()
         length = min(maxy - 1, len(output))
         for y in range(0, length):
             line = output[y]
             if diffcolors:
                 if line and line[0] == b'+':
                     win.addstr(
                         y, 0, line, curses.color_pair(COLOR_DIFF_ADD_LINE)
                     )
                 elif line and line[0] == b'-':
                     win.addstr(
                         y, 0, line, curses.color_pair(COLOR_DIFF_DEL_LINE)
                     )
                 elif line.startswith(b'@@ '):
                     win.addstr(y, 0, line, curses.color_pair(COLOR_DIFF_OFFSET))
                 else:
                     win.addstr(y, 0, line)
             else:
                 win.addstr(y, 0, line)
         win.noutrefresh()
 
     def renderpatch(win, state):
         start = state[b'modes'][MODE_PATCH][b'line_offset']
         content = state[b'modes'][MODE_PATCH][b'patchcontents']
         renderstring(win, state, content[start:], diffcolors=True)
 
     def layout(mode):
         maxy, maxx = stdscr.getmaxyx()
         helplen = len(helplines(mode))
         return {
             b'commit': (12, maxx),
             b'help': (helplen, maxx),
             b'main': (maxy - helplen - 12, maxx),
         }
 
     def drawvertwin(size, y, x):
         win = curses.newwin(size[0], size[1], y, x)
         y += size[0]
         return win, y, x
 
     state = {
         b'pos': 0,
         b'rules': rules,
         b'selected': None,
         b'mode': (MODE_INIT, MODE_INIT),
         b'page_height': None,
         b'modes': {
             MODE_RULES: {b'line_offset': 0,},
             MODE_PATCH: {b'line_offset': 0,},
         },
         b'repo': repo,
     }
 
     # eventloop
     ch = None
     stdscr.clear()
     stdscr.refresh()
     while True:
         try:
             oldmode, _ = state[b'mode']
             if oldmode == MODE_INIT:
                 changemode(state, MODE_RULES)
             e = event(state, ch)
 
             if e == E_QUIT:
                 return False
             if e == E_HISTEDIT:
                 return state[b'rules']
             else:
                 if e == E_RESIZE:
                     size = screen_size()
                     if size != stdscr.getmaxyx():
                         curses.resizeterm(*size)
 
                 curmode, _ = state[b'mode']
                 sizes = layout(curmode)
                 if curmode != oldmode:
                     state[b'page_height'] = sizes[b'main'][0]
                     # Adjust the view to fit the current screen size.
                     movecursor(state, state[b'pos'], state[b'pos'])
 
                 # Pack the windows against the top, each pane spread across the
                 # full width of the screen.
                 y, x = (0, 0)
                 helpwin, y, x = drawvertwin(sizes[b'help'], y, x)
                 mainwin, y, x = drawvertwin(sizes[b'main'], y, x)
                 commitwin, y, x = drawvertwin(sizes[b'commit'], y, x)
 
                 if e in (E_PAGEDOWN, E_PAGEUP, E_LINEDOWN, E_LINEUP):
                     if e == E_PAGEDOWN:
                         changeview(state, +1, b'page')
                     elif e == E_PAGEUP:
                         changeview(state, -1, b'page')
                     elif e == E_LINEDOWN:
                         changeview(state, +1, b'line')
                     elif e == E_LINEUP:
                         changeview(state, -1, b'line')
 
                 # start rendering
                 commitwin.erase()
                 helpwin.erase()
                 mainwin.erase()
                 if curmode == MODE_PATCH:
                     renderpatch(mainwin, state)
                 elif curmode == MODE_HELP:
                     renderstring(mainwin, state, __doc__.strip().splitlines())
                 else:
                     renderrules(mainwin, state)
                     rendercommit(commitwin, state)
                 renderhelp(helpwin, state)
                 curses.doupdate()
                 # done rendering
                 ch = encoding.strtolocal(stdscr.getkey())
         except curses.error:
             pass
 
 
 def _chistedit(ui, repo, freeargs, opts):
     """interactively edit changeset history via a curses interface
 
     Provides a ncurses interface to histedit. Press ? in chistedit mode
     to see an extensive help. Requires python-curses to be installed."""
 
     if curses is None:
         raise error.Abort(_(b"Python curses library required"))
 
     # disable color
     ui._colormode = None
 
     try:
         keep = opts.get(b'keep')
         revs = opts.get(b'rev', [])[:]
         cmdutil.checkunfinished(repo)
         cmdutil.bailifchanged(repo)
 
         if os.path.exists(os.path.join(repo.path, b'histedit-state')):
             raise error.Abort(
                 _(
                     b'history edit already in progress, try '
                     b'--continue or --abort'
                 )
             )
         revs.extend(freeargs)
         if not revs:
             defaultrev = destutil.desthistedit(ui, repo)
             if defaultrev is not None:
                 revs.append(defaultrev)
         if len(revs) != 1:
             raise error.Abort(
                 _(b'histedit requires exactly one ancestor revision')
             )
 
         rr = list(repo.set(b'roots(%ld)', scmutil.revrange(repo, revs)))
         if len(rr) != 1:
             raise error.Abort(
                 _(
                     b'The specified revisions must have '
                     b'exactly one common root'
                 )
             )
         root = rr[0].node()
 
         topmost = repo.dirstate.p1()
         revs = between(repo, root, topmost, keep)
         if not revs:
             raise error.Abort(
                 _(b'%s is not an ancestor of working directory')
                 % node.short(root)
             )
 
         ctxs = []
         for i, r in enumerate(revs):
             ctxs.append(histeditrule(ui, repo[r], i))
         with util.with_lc_ctype():
             rc = curses.wrapper(functools.partial(_chisteditmain, repo, ctxs))
         curses.echo()
         curses.endwin()
         if rc is False:
             ui.write(_(b"histedit aborted\n"))
             return 0
         if type(rc) is list:
             ui.status(_(b"performing changes\n"))
             rules = makecommands(rc)
             with repo.vfs(b'chistedit', b'w+') as fp:
                 for r in rules:
                     fp.write(r)
                 opts[b'commands'] = fp.name
             return _texthistedit(ui, repo, freeargs, opts)
     except KeyboardInterrupt:
         pass
     return -1
 
 
 @command(
     b'histedit',
     [
         (
             b'',
             b'commands',
             b'',
             _(b'read history edits from the specified file'),
             _(b'FILE'),
         ),
         (b'c', b'continue', False, _(b'continue an edit already in progress')),
         (b'', b'edit-plan', False, _(b'edit remaining actions list')),
         (
             b'k',
             b'keep',
             False,
             _(b"don't strip old nodes after edit is complete"),
         ),
         (b'', b'abort', False, _(b'abort an edit in progress')),
         (b'o', b'outgoing', False, _(b'changesets not found in destination')),
         (
             b'f',
             b'force',
             False,
             _(b'force outgoing even for unrelated repositories'),
         ),
         (b'r', b'rev', [], _(b'first revision to be edited'), _(b'REV')),
     ]
     + cmdutil.formatteropts,
     _(b"[OPTIONS] ([ANCESTOR] | --outgoing [URL])"),
     helpcategory=command.CATEGORY_CHANGE_MANAGEMENT,
 )
 def histedit(ui, repo, *freeargs, **opts):
     """interactively edit changeset history
 
     This command lets you edit a linear series of changesets (up to
     and including the working directory, which should be clean).
     You can:
 
     - `pick` to [re]order a changeset
 
     - `drop` to omit changeset
 
     - `mess` to reword the changeset commit message
 
     - `fold` to combine it with the preceding changeset (using the later date)
 
     - `roll` like fold, but discarding this commit's description and date
 
     - `edit` to edit this changeset (preserving date)
 
     - `base` to checkout changeset and apply further changesets from there
 
     There are a number of ways to select the root changeset:
 
     - Specify ANCESTOR directly
 
     - Use --outgoing -- it will be the first linear changeset not
       included in destination. (See :hg:`help config.paths.default-push`)
 
     - Otherwise, the value from the "histedit.defaultrev" config option
       is used as a revset to select the base revision when ANCESTOR is not
       specified. The first revision returned by the revset is used. By
       default, this selects the editable history that is unique to the
       ancestry of the working directory.
 
     .. container:: verbose
 
        If you use --outgoing, this command will abort if there are ambiguous
        outgoing revisions. For example, if there are multiple branches
        containing outgoing revisions.
 
        Use "min(outgoing() and ::.)" or similar revset specification
        instead of --outgoing to specify edit target revision exactly in
        such ambiguous situation. See :hg:`help revsets` for detail about
        selecting revisions.
 
     .. container:: verbose
 
        Examples:
 
          - A number of changes have been made.
            Revision 3 is no longer needed.
 
            Start history editing from revision 3::
 
              hg histedit -r 3
 
            An editor opens, containing the list of revisions,
            with specific actions specified::
 
              pick 5339bf82f0ca 3 Zworgle the foobar
              pick 8ef592ce7cc4 4 Bedazzle the zerlog
              pick 0a9639fcda9d 5 Morgify the cromulancy
 
            Additional information about the possible actions
            to take appears below the list of revisions.
 
            To remove revision 3 from the history,
            its action (at the beginning of the relevant line)
            is changed to 'drop'::
 
              drop 5339bf82f0ca 3 Zworgle the foobar
              pick 8ef592ce7cc4 4 Bedazzle the zerlog
              pick 0a9639fcda9d 5 Morgify the cromulancy
 
          - A number of changes have been made.
            Revision 2 and 4 need to be swapped.
 
            Start history editing from revision 2::
 
              hg histedit -r 2
 
            An editor opens, containing the list of revisions,
            with specific actions specified::
 
              pick 252a1af424ad 2 Blorb a morgwazzle
              pick 5339bf82f0ca 3 Zworgle the foobar
              pick 8ef592ce7cc4 4 Bedazzle the zerlog
 
            To swap revision 2 and 4, its lines are swapped
            in the editor::
 
              pick 8ef592ce7cc4 4 Bedazzle the zerlog
              pick 5339bf82f0ca 3 Zworgle the foobar
              pick 252a1af424ad 2 Blorb a morgwazzle
 
     Returns 0 on success, 1 if user intervention is required (not only
     for intentional "edit" command, but also for resolving unexpected
     conflicts).
     """
     opts = pycompat.byteskwargs(opts)
 
     # kludge: _chistedit only works for starting an edit, not aborting
     # or continuing, so fall back to regular _texthistedit for those
     # operations.
     if ui.interface(b'histedit') == b'curses' and _getgoal(opts) == goalnew:
         return _chistedit(ui, repo, freeargs, opts)
     return _texthistedit(ui, repo, freeargs, opts)
 
 
 def _texthistedit(ui, repo, freeargs, opts):
     state = histeditstate(repo)
     with repo.wlock() as wlock, repo.lock() as lock:
         state.wlock = wlock
         state.lock = lock
         _histedit(ui, repo, state, freeargs, opts)
 
 
 goalcontinue = b'continue'
 goalabort = b'abort'
 goaleditplan = b'edit-plan'
 goalnew = b'new'
 
 
 def _getgoal(opts):
     if opts.get(b'continue'):
         return goalcontinue
     if opts.get(b'abort'):
         return goalabort
     if opts.get(b'edit_plan'):
         return goaleditplan
     return goalnew
 
 
 def _readfile(ui, path):
     if path == b'-':
         with ui.timeblockedsection(b'histedit'):
             return ui.fin.read()
     else:
         with open(path, b'rb') as f:
             return f.read()
 
 
 def _validateargs(ui, repo, state, freeargs, opts, goal, rules, revs):
     # TODO only abort if we try to histedit mq patches, not just
     # blanket if mq patches are applied somewhere
     mq = getattr(repo, 'mq', None)
     if mq and mq.applied:
         raise error.Abort(_(b'source has mq patches applied'))
 
     # basic argument incompatibility processing
     outg = opts.get(b'outgoing')
     editplan = opts.get(b'edit_plan')
     abort = opts.get(b'abort')
     force = opts.get(b'force')
     if force and not outg:
         raise error.Abort(_(b'--force only allowed with --outgoing'))
     if goal == b'continue':
         if any((outg, abort, revs, freeargs, rules, editplan)):
             raise error.Abort(_(b'no arguments allowed with --continue'))
     elif goal == b'abort':
         if any((outg, revs, freeargs, rules, editplan)):
             raise error.Abort(_(b'no arguments allowed with --abort'))
     elif goal == b'edit-plan':
         if any((outg, revs, freeargs)):
             raise error.Abort(
                 _(b'only --commands argument allowed with --edit-plan')
             )
     else:
         if state.inprogress():
             raise error.Abort(
                 _(
                     b'history edit already in progress, try '
                     b'--continue or --abort'
                 )
             )
         if outg:
             if revs:
                 raise error.Abort(_(b'no revisions allowed with --outgoing'))
             if len(freeargs) > 1:
                 raise error.Abort(
                     _(b'only one repo argument allowed with --outgoing')
                 )
         else:
             revs.extend(freeargs)
             if len(revs) == 0:
                 defaultrev = destutil.desthistedit(ui, repo)
                 if defaultrev is not None:
                     revs.append(defaultrev)
 
             if len(revs) != 1:
                 raise error.Abort(
                     _(b'histedit requires exactly one ancestor revision')
                 )
 
 
 def _histedit(ui, repo, state, freeargs, opts):
     fm = ui.formatter(b'histedit', opts)
     fm.startitem()
     goal = _getgoal(opts)
     revs = opts.get(b'rev', [])
     nobackup = not ui.configbool(b'rewrite', b'backup-bundle')
     rules = opts.get(b'commands', b'')
     state.keep = opts.get(b'keep', False)
 
     _validateargs(ui, repo, state, freeargs, opts, goal, rules, revs)
 
     hastags = False
     if revs:
         revs = scmutil.revrange(repo, revs)
         ctxs = [repo[rev] for rev in revs]
         for ctx in ctxs:
             tags = [tag for tag in ctx.tags() if tag != b'tip']
             if not hastags:
                 hastags = len(tags)
     if hastags:
         if ui.promptchoice(
             _(
                 b'warning: tags associated with the given'
                 b' changeset will be lost after histedit.\n'
                 b'do you want to continue (yN)? $$ &Yes $$ &No'
             ),
             default=1,
         ):
             raise error.Abort(_(b'histedit cancelled\n'))
     # rebuild state
     if goal == goalcontinue:
         state.read()
         state = bootstrapcontinue(ui, state, opts)
     elif goal == goaleditplan:
         _edithisteditplan(ui, repo, state, rules)
         return
     elif goal == goalabort:
         _aborthistedit(ui, repo, state, nobackup=nobackup)
         return
     else:
         # goal == goalnew
         _newhistedit(ui, repo, state, revs, freeargs, opts)
 
     _continuehistedit(ui, repo, state)
     _finishhistedit(ui, repo, state, fm)
     fm.end()
 
 
 def _continuehistedit(ui, repo, state):
     """This function runs after either:
     - bootstrapcontinue (if the goal is 'continue')
     - _newhistedit (if the goal is 'new')
     """
     # preprocess rules so that we can hide inner folds from the user
     # and only show one editor
     actions = state.actions[:]
     for idx, (action, nextact) in enumerate(zip(actions, actions[1:] + [None])):
         if action.verb == b'fold' and nextact and nextact.verb == b'fold':
             state.actions[idx].__class__ = _multifold
 
     # Force an initial state file write, so the user can run --abort/continue
     # even if there's an exception before the first transaction serialize.
     state.write()
 
     tr = None
     # Don't use singletransaction by default since it rolls the entire
     # transaction back if an unexpected exception happens (like a
     # pretxncommit hook throws, or the user aborts the commit msg editor).
     if ui.configbool(b"histedit", b"singletransaction"):
         # Don't use a 'with' for the transaction, since actions may close
         # and reopen a transaction. For example, if the action executes an
         # external process it may choose to commit the transaction first.
         tr = repo.transaction(b'histedit')
     progress = ui.makeprogress(
         _(b"editing"), unit=_(b'changes'), total=len(state.actions)
     )
     with progress, util.acceptintervention(tr):
         while state.actions:
             state.write(tr=tr)
             actobj = state.actions[0]
             progress.increment(item=actobj.torule())
             ui.debug(
                 b'histedit: processing %s %s\n' % (actobj.verb, actobj.torule())
             )
             parentctx, replacement_ = actobj.run()
             state.parentctxnode = parentctx.node()
             state.replacements.extend(replacement_)
             state.actions.pop(0)
 
     state.write()
 
 
 def _finishhistedit(ui, repo, state, fm):
     """This action runs when histedit is finishing its session"""
     mergemod.update(repo[state.parentctxnode])
 
     mapping, tmpnodes, created, ntm = processreplacement(state)
     if mapping:
         for prec, succs in pycompat.iteritems(mapping):
             if not succs:
                 ui.debug(b'histedit: %s is dropped\n' % node.short(prec))
             else:
                 ui.debug(
                     b'histedit: %s is replaced by %s\n'
                     % (node.short(prec), node.short(succs[0]))
                 )
                 if len(succs) > 1:
                     m = b'histedit:                            %s'
                     for n in succs[1:]:
                         ui.debug(m % node.short(n))
 
     if not state.keep:
         if mapping:
             movetopmostbookmarks(repo, state.topmost, ntm)
             # TODO update mq state
     else:
         mapping = {}
 
     for n in tmpnodes:
         if n in repo:
             mapping[n] = ()
 
     # remove entries about unknown nodes
     has_node = repo.unfiltered().changelog.index.has_node
     mapping = {
         k: v
         for k, v in mapping.items()
         if has_node(k) and all(has_node(n) for n in v)
     }
     scmutil.cleanupnodes(repo, mapping, b'histedit')
     hf = fm.hexfunc
     fl = fm.formatlist
     fd = fm.formatdict
     nodechanges = fd(
         {
             hf(oldn): fl([hf(n) for n in newn], name=b'node')
             for oldn, newn in pycompat.iteritems(mapping)
         },
         key=b"oldnode",
         value=b"newnodes",
     )
     fm.data(nodechanges=nodechanges)
 
     state.clear()
     if os.path.exists(repo.sjoin(b'undo')):
         os.unlink(repo.sjoin(b'undo'))
     if repo.vfs.exists(b'histedit-last-edit.txt'):
         repo.vfs.unlink(b'histedit-last-edit.txt')
 
 
 def _aborthistedit(ui, repo, state, nobackup=False):
     try:
         state.read()
         __, leafs, tmpnodes, __ = processreplacement(state)
         ui.debug(b'restore wc to old parent %s\n' % node.short(state.topmost))
 
         # Recover our old commits if necessary
         if not state.topmost in repo and state.backupfile:
             backupfile = repo.vfs.join(state.backupfile)
             f = hg.openpath(ui, backupfile)
             gen = exchange.readbundle(ui, f, backupfile)
             with repo.transaction(b'histedit.abort') as tr:
                 bundle2.applybundle(
                     repo,
                     gen,
                     tr,
                     source=b'histedit',
                     url=b'bundle:' + backupfile,
                 )
 
             os.remove(backupfile)
 
         # check whether we should update away
         if repo.unfiltered().revs(
             b'parents() and (%n  or %ln::)',
             state.parentctxnode,
             leafs | tmpnodes,
         ):
             hg.clean(repo, state.topmost, show_stats=True, quietempty=True)
         cleanupnode(ui, repo, tmpnodes, nobackup=nobackup)
         cleanupnode(ui, repo, leafs, nobackup=nobackup)
     except Exception:
         if state.inprogress():
             ui.warn(
                 _(
                     b'warning: encountered an exception during histedit '
                     b'--abort; the repository may not have been completely '
                     b'cleaned up\n'
                 )
             )
         raise
     finally:
         state.clear()
 
 
 def hgaborthistedit(ui, repo):
     state = histeditstate(repo)
     nobackup = not ui.configbool(b'rewrite', b'backup-bundle')
     with repo.wlock() as wlock, repo.lock() as lock:
         state.wlock = wlock
         state.lock = lock
         _aborthistedit(ui, repo, state, nobackup=nobackup)
 
 
 def _edithisteditplan(ui, repo, state, rules):
     state.read()
     if not rules:
         comment = geteditcomment(
             ui, node.short(state.parentctxnode), node.short(state.topmost)
         )
         rules = ruleeditor(repo, ui, state.actions, comment)
     else:
         rules = _readfile(ui, rules)
     actions = parserules(rules, state)
     ctxs = [repo[act.node] for act in state.actions if act.node]
     warnverifyactions(ui, repo, actions, state, ctxs)
     state.actions = actions
     state.write()
 
 
 def _newhistedit(ui, repo, state, revs, freeargs, opts):
     outg = opts.get(b'outgoing')
     rules = opts.get(b'commands', b'')
     force = opts.get(b'force')
 
     cmdutil.checkunfinished(repo)
     cmdutil.bailifchanged(repo)
 
     topmost = repo.dirstate.p1()
     if outg:
         if freeargs:
             remote = freeargs[0]
         else:
             remote = None
         root = findoutgoing(ui, repo, remote, force, opts)
     else:
         rr = list(repo.set(b'roots(%ld)', scmutil.revrange(repo, revs)))
         if len(rr) != 1:
             raise error.Abort(
                 _(
                     b'The specified revisions must have '
                     b'exactly one common root'
                 )
             )
         root = rr[0].node()
 
     revs = between(repo, root, topmost, state.keep)
     if not revs:
         raise error.Abort(
             _(b'%s is not an ancestor of working directory') % node.short(root)
         )
 
     ctxs = [repo[r] for r in revs]
 
     wctx = repo[None]
     # Please don't ask me why `ancestors` is this value. I figured it
     # out with print-debugging, not by actually understanding what the
     # merge code is doing. :(
     ancs = [repo[b'.']]
     # Sniff-test to make sure we won't collide with untracked files in
     # the working directory. If we don't do this, we can get a
     # collision after we've started histedit and backing out gets ugly
     # for everyone, especially the user.
     for c in [ctxs[0].p1()] + ctxs:
         try:
             mergemod.calculateupdates(
                 repo,
                 wctx,
                 c,
                 ancs,
                 # These parameters were determined by print-debugging
                 # what happens later on inside histedit.
                 branchmerge=False,
                 force=False,
                 acceptremote=False,
                 followcopies=False,
             )
         except error.Abort:
             raise error.Abort(
                 _(
                     b"untracked files in working directory conflict with files in %s"
                 )
                 % c
             )
 
     if not rules:
         comment = geteditcomment(ui, node.short(root), node.short(topmost))
         actions = [pick(state, r) for r in revs]
         rules = ruleeditor(repo, ui, actions, comment)
     else:
         rules = _readfile(ui, rules)
     actions = parserules(rules, state)
     warnverifyactions(ui, repo, actions, state, ctxs)
 
     parentctxnode = repo[root].p1().node()
 
     state.parentctxnode = parentctxnode
     state.actions = actions
     state.topmost = topmost
     state.replacements = []
 
     ui.log(
         b"histedit",
         b"%d actions to histedit\n",
         len(actions),
         histedit_num_actions=len(actions),
     )
 
     # Create a backup so we can always abort completely.
     backupfile = None
     if not obsolete.isenabled(repo, obsolete.createmarkersopt):
         backupfile = repair.backupbundle(
             repo, [parentctxnode], [topmost], root, b'histedit'
         )
     state.backupfile = backupfile
 
 
 def _getsummary(ctx):
     # a common pattern is to extract the summary but default to the empty
     # string
     summary = ctx.description() or b''
     if summary:
         summary = summary.splitlines()[0]
     return summary
 
 
 def bootstrapcontinue(ui, state, opts):
     repo = state.repo
 
     ms = mergestatemod.mergestate.read(repo)
     mergeutil.checkunresolved(ms)
 
     if state.actions:
         actobj = state.actions.pop(0)
 
         if _isdirtywc(repo):
             actobj.continuedirty()
             if _isdirtywc(repo):
                 abortdirty()
 
         parentctx, replacements = actobj.continueclean()
 
         state.parentctxnode = parentctx.node()
         state.replacements.extend(replacements)
 
     return state
 
 
 def between(repo, old, new, keep):
     """select and validate the set of revision to edit
 
     When keep is false, the specified set can't have children."""
     revs = repo.revs(b'%n::%n', old, new)
     if revs and not keep:
         rewriteutil.precheck(repo, revs, b'edit')
         if repo.revs(b'(%ld) and merge()', revs):
             raise error.Abort(_(b'cannot edit history that contains merges'))
     return pycompat.maplist(repo.changelog.node, revs)
 
 
 def ruleeditor(repo, ui, actions, editcomment=b""):
     """open an editor to edit rules
 
     rules are in the format [ [act, ctx], ...] like in state.rules
     """
     if repo.ui.configbool(b"experimental", b"histedit.autoverb"):
         newact = util.sortdict()
         for act in actions:
             ctx = repo[act.node]
             summary = _getsummary(ctx)
             fword = summary.split(b' ', 1)[0].lower()
             added = False
 
             # if it doesn't end with the special character '!' just skip this
             if fword.endswith(b'!'):
                 fword = fword[:-1]
                 if fword in primaryactions | secondaryactions | tertiaryactions:
                     act.verb = fword
                     # get the target summary
                     tsum = summary[len(fword) + 1 :].lstrip()
                     # safe but slow: reverse iterate over the actions so we
                     # don't clash on two commits having the same summary
                     for na, l in reversed(list(pycompat.iteritems(newact))):
                         actx = repo[na.node]
                         asum = _getsummary(actx)
                         if asum == tsum:
                             added = True
                             l.append(act)
                             break
 
             if not added:
                 newact[act] = []
 
         # copy over and flatten the new list
         actions = []
         for na, l in pycompat.iteritems(newact):
             actions.append(na)
             actions += l
 
     rules = b'\n'.join([act.torule() for act in actions])
     rules += b'\n\n'
     rules += editcomment
     rules = ui.edit(
         rules,
         ui.username(),
         {b'prefix': b'histedit'},
         repopath=repo.path,
         action=b'histedit',
     )
 
     # Save edit rules in .hg/histedit-last-edit.txt in case
     # the user needs to ask for help after something
     # surprising happens.
     with repo.vfs(b'histedit-last-edit.txt', b'wb') as f:
         f.write(rules)
 
     return rules
 
 
 def parserules(rules, state):
     """Read the histedit rules string and return list of action objects """
     rules = [
         l
         for l in (r.strip() for r in rules.splitlines())
         if l and not l.startswith(b'#')
     ]
     actions = []
     for r in rules:
         if b' ' not in r:
             raise error.ParseError(_(b'malformed line "%s"') % r)
         verb, rest = r.split(b' ', 1)
 
         if verb not in actiontable:
             raise error.ParseError(_(b'unknown action "%s"') % verb)
 
         action = actiontable[verb].fromrule(state, rest)
         actions.append(action)
     return actions
 
 
 def warnverifyactions(ui, repo, actions, state, ctxs):
     try:
         verifyactions(actions, state, ctxs)
     except error.ParseError:
         if repo.vfs.exists(b'histedit-last-edit.txt'):
             ui.warn(
                 _(
                     b'warning: histedit rules saved '
                     b'to: .hg/histedit-last-edit.txt\n'
                 )
             )
         raise
 
 
 def verifyactions(actions, state, ctxs):
     """Verify that there exists exactly one action per given changeset and
     other constraints.
 
     Will abort if there are to many or too few rules, a malformed rule,
     or a rule on a changeset outside of the user-given range.
     """
     expected = {c.node() for c in ctxs}
     seen = set()
     prev = None
 
     if actions and actions[0].verb in [b'roll', b'fold']:
         raise error.ParseError(
             _(b'first changeset cannot use verb "%s"') % actions[0].verb
         )
 
     for action in actions:
         action.verify(prev, expected, seen)
         prev = action
         if action.node is not None:
             seen.add(action.node)
     missing = sorted(expected - seen)  # sort to stabilize output
 
     if state.repo.ui.configbool(b'histedit', b'dropmissing'):
         if len(actions) == 0:
             raise error.ParseError(
                 _(b'no rules provided'),
                 hint=_(b'use strip extension to remove commits'),
             )
 
         drops = [drop(state, n) for n in missing]
         # put the in the beginning so they execute immediately and
         # don't show in the edit-plan in the future
         actions[:0] = drops
     elif missing:
         raise error.ParseError(
             _(b'missing rules for changeset %s') % node.short(missing[0]),
             hint=_(
                 b'use "drop %s" to discard, see also: '
                 b"'hg help -e histedit.config'"
             )
             % node.short(missing[0]),
         )
 
 
 def adjustreplacementsfrommarkers(repo, oldreplacements):
     """Adjust replacements from obsolescence markers
 
     Replacements structure is originally generated based on
     histedit's state and does not account for changes that are
     not recorded there. This function fixes that by adding
     data read from obsolescence markers"""
     if not obsolete.isenabled(repo, obsolete.createmarkersopt):
         return oldreplacements
 
     unfi = repo.unfiltered()
     get_rev = unfi.changelog.index.get_rev
     obsstore = repo.obsstore
     newreplacements = list(oldreplacements)
     oldsuccs = [r[1] for r in oldreplacements]
     # successors that have already been added to succstocheck once
     seensuccs = set().union(
         *oldsuccs
     )  # create a set from an iterable of tuples
     succstocheck = list(seensuccs)
     while succstocheck:
         n = succstocheck.pop()
         missing = get_rev(n) is None
         markers = obsstore.successors.get(n, ())
         if missing and not markers:
             # dead end, mark it as such
             newreplacements.append((n, ()))
         for marker in markers:
             nsuccs = marker[1]
             newreplacements.append((n, nsuccs))
             for nsucc in nsuccs:
                 if nsucc not in seensuccs:
                     seensuccs.add(nsucc)
                     succstocheck.append(nsucc)
 
     return newreplacements
 
 
 def processreplacement(state):
     """process the list of replacements to return
 
     1) the final mapping between original and created nodes
     2) the list of temporary node created by histedit
     3) the list of new commit created by histedit"""
     replacements = adjustreplacementsfrommarkers(state.repo, state.replacements)
     allsuccs = set()
     replaced = set()
     fullmapping = {}
     # initialize basic set
     # fullmapping records all operations recorded in replacement
     for rep in replacements:
         allsuccs.update(rep[1])
         replaced.add(rep[0])
         fullmapping.setdefault(rep[0], set()).update(rep[1])
     new = allsuccs - replaced
     tmpnodes = allsuccs & replaced
     # Reduce content fullmapping into direct relation between original nodes
     # and final node created during history edition
     # Dropped changeset are replaced by an empty list
     toproceed = set(fullmapping)
     final = {}
     while toproceed:
         for x in list(toproceed):
             succs = fullmapping[x]
             for s in list(succs):
                 if s in toproceed:
                     # non final node with unknown closure
                     # We can't process this now
                     break
                 elif s in final:
                     # non final node, replace with closure
                     succs.remove(s)
                     succs.update(final[s])
             else:
                 final[x] = succs
                 toproceed.remove(x)
     # remove tmpnodes from final mapping
     for n in tmpnodes:
         del final[n]
     # we expect all changes involved in final to exist in the repo
     # turn `final` into list (topologically sorted)
     get_rev = state.repo.changelog.index.get_rev
     for prec, succs in final.items():
         final[prec] = sorted(succs, key=get_rev)
 
     # computed topmost element (necessary for bookmark)
     if new:
         newtopmost = sorted(new, key=state.repo.changelog.rev)[-1]
     elif not final:
         # Nothing rewritten at all. we won't need `newtopmost`
         # It is the same as `oldtopmost` and `processreplacement` know it
         newtopmost = None
     else:
         # every body died. The newtopmost is the parent of the root.
         r = state.repo.changelog.rev
         newtopmost = state.repo[sorted(final, key=r)[0]].p1().node()
 
     return final, tmpnodes, new, newtopmost
 
 
 def movetopmostbookmarks(repo, oldtopmost, newtopmost):
     """Move bookmark from oldtopmost to newly created topmost
 
     This is arguably a feature and we may only want that for the active
     bookmark. But the behavior is kept compatible with the old version for now.
     """
     if not oldtopmost or not newtopmost:
         return
     oldbmarks = repo.nodebookmarks(oldtopmost)
     if oldbmarks:
         with repo.lock(), repo.transaction(b'histedit') as tr:
             marks = repo._bookmarks
             changes = []
             for name in oldbmarks:
                 changes.append((name, newtopmost))
             marks.applychanges(repo, tr, changes)
 
 
 def cleanupnode(ui, repo, nodes, nobackup=False):
     """strip a group of nodes from the repository
 
     The set of node to strip may contains unknown nodes."""
     with repo.lock():
         # do not let filtering get in the way of the cleanse
         # we should probably get rid of obsolescence marker created during the
         # histedit, but we currently do not have such information.
         repo = repo.unfiltered()
         # Find all nodes that need to be stripped
         # (we use %lr instead of %ln to silently ignore unknown items)
         has_node = repo.changelog.index.has_node
         nodes = sorted(n for n in nodes if has_node(n))
         roots = [c.node() for c in repo.set(b"roots(%ln)", nodes)]
         if roots:
             backup = not nobackup
             repair.strip(ui, repo, roots, backup=backup)
 
 
 def stripwrapper(orig, ui, repo, nodelist, *args, **kwargs):
     if isinstance(nodelist, bytes):
         nodelist = [nodelist]
     state = histeditstate(repo)
     if state.inprogress():
         state.read()
         histedit_nodes = {
             action.node for action in state.actions if action.node
         }
         common_nodes = histedit_nodes & set(nodelist)
         if common_nodes:
             raise error.Abort(
                 _(b"histedit in progress, can't strip %s")
                 % b', '.join(node.short(x) for x in common_nodes)
             )
     return orig(ui, repo, nodelist, *args, **kwargs)
 
 
 extensions.wrapfunction(repair, b'strip', stripwrapper)
 
 
 def summaryhook(ui, repo):
     state = histeditstate(repo)
     if not state.inprogress():
         return
     state.read()
     if state.actions:
         # i18n: column positioning for "hg summary"
         ui.write(
             _(b'hist:   %s (histedit --continue)\n')
             % (
                 ui.label(_(b'%d remaining'), b'histedit.remaining')
                 % len(state.actions)
             )
         )
 
 
 def extsetup(ui):
     cmdutil.summaryhooks.add(b'histedit', summaryhook)
     statemod.addunfinished(
         b'histedit',
         fname=b'histedit-state',
         allowcommit=True,
         continueflag=True,
         abortfunc=hgaborthistedit,
     )