histedit: more precise user message when changeset is missing

Now that we explicitly detect duplicated changesets, we can explicitly
detect missing ones. We cover the same cases as before, some others
and we offer a better error message in all cases.

hgext/histedit.py

@@ -1,856 +1,858 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
  #
  # Commands:
  #  p, pick = use commit
  #  e, edit = use commit, but stop for amending
  #  f, fold = use commit, but fold into previous commit (combines N and N-1)
  #  d, drop = remove commit from history
  #  m, mess = edit message without changing commit content
  #
 
 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
  #
  # Commands:
  #  p, pick = use commit
  #  e, edit = use commit, but stop for amending
  #  f, fold = use commit, but fold into previous commit (combines N and N-1)
  #  d, drop = remove commit from history
  #  m, mess = edit message without changing commit content
  #
 
 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. 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. You'll be prompted for a
 new commit message, but the default commit message will be the
 original message for the ``edit`` ed revision.
 
 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.
 """
 
 try:
     import cPickle as pickle
 except ImportError:
     import pickle
 import os
 import sys
 
 from mercurial import cmdutil
 from mercurial import discovery
 from mercurial import error
 from mercurial import copies
 from mercurial import context
 from mercurial import hg
 from mercurial import lock as lockmod
 from mercurial import node
 from mercurial import repair
 from mercurial import scmutil
 from mercurial import util
 from mercurial import obsolete
 from mercurial import merge as mergemod
 from mercurial.i18n import _
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
 
 testedwith = 'internal'
 
 # i18n: command names and abbreviations must remain untranslated
 editcomment = _("""# Edit history between %s and %s
 #
 # Commands:
 #  p, pick = use commit
 #  e, edit = use commit, but stop for amending
 #  f, fold = use commit, but fold into previous commit (combines N and N-1)
 #  d, drop = remove commit from history
 #  m, mess = edit message without changing commit content
 #
 """)
 
 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 have 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):
         phasebackup = repo.ui.backupconfig('phases', 'new-commit')
         try:
             repo.ui.setconfig('phases', 'new-commit', phasemin)
             extra = kwargs.get('extra', {}).copy()
             extra['histedit_source'] = src.hex()
             kwargs['extra'] = extra
             return repo.commit(**kwargs)
         finally:
             repo.ui.restoreconfig(phasebackup)
     return commitfunc
 
 
 
 def applychanges(ui, repo, ctx, opts):
     """Merge changeset from ctx (only) in the current working directory"""
     wcpar = repo.dirstate.parents()[0]
     if ctx.p1().node() == wcpar:
         # edition ar "in place" we do not need to make any merge,
         # just applies changes on parent for edition
         cmdutil.revert(ui, repo, ctx, (wcpar, node.nullid), all=True)
         stats = None
     else:
         try:
             # ui.forcemerge is an internal variable, do not document
             repo.ui.setconfig('ui', 'forcemerge', opts.get('tool', ''))
             stats = mergemod.update(repo, ctx.node(), True, True, False,
                                     ctx.p1().node())
         finally:
             repo.ui.setconfig('ui', 'forcemerge', '')
         repo.setparents(wcpar, node.nullid)
         repo.dirstate.write()
         # fix up dirstate for copies and renames
     cmdutil.duplicatecopies(repo, ctx.rev(), ctx.p1().rev())
     return stats
 
 def collapse(repo, first, last, commitopts):
     """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('%d::%d', first, last))
     if not ctxs:
         return None
     base = first.parents()[0]
 
     # 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(first, last)
 
     # prune files which were reverted by the updates
     def samefile(f):
         if f in last.manifest():
             a = last.filectx(f)
             if f in base.manifest():
                 b = base.filectx(f)
                 return (a.data() == b.data()
                         and a.flags() == b.flags())
             else:
                 return False
         else:
             return f not in base.manifest()
     files = [f for f in files if not samefile(f)]
     # commit version of these files as defined by head
     headmf = last.manifest()
     def filectxfn(repo, ctx, path):
         if path in headmf:
             fctx = last[path]
             flags = fctx.flags()
             mctx = context.memfilectx(fctx.path(), fctx.data(),
                                       islink='l' in flags,
                                       isexec='x' in flags,
                                       copied=copied.get(path))
             return mctx
         raise IOError()
 
     if commitopts.get('message'):
         message = commitopts['message']
     else:
         message = first.description()
     user = commitopts.get('user')
     date = commitopts.get('date')
     extra = commitopts.get('extra')
 
     parents = (first.p1().node(), first.p2().node())
     new = context.memctx(repo,
                          parents=parents,
                          text=message,
                          files=files,
                          filectxfn=filectxfn,
                          user=user,
                          date=date,
                          extra=extra)
     new._text = cmdutil.commitforceeditor(repo, new, [])
     return repo.commitctx(new)
 
 def pick(ui, repo, ctx, ha, opts):
     oldctx = repo[ha]
     if oldctx.parents()[0] == ctx:
         ui.debug('node %s unchanged\n' % ha)
         return oldctx, []
     hg.update(repo, ctx.node())
     stats = applychanges(ui, repo, oldctx, opts)
     if stats and stats[3] > 0:
         raise error.InterventionRequired(_('Fix up the change and run '
                                            'hg histedit --continue'))
     # drop the second merge parent
     commit = commitfuncfor(repo, oldctx)
     n = commit(text=oldctx.description(), user=oldctx.user(),
                date=oldctx.date(), extra=oldctx.extra())
     if n is None:
         ui.warn(_('%s: empty changeset\n')
                      % node.hex(ha))
         return ctx, []
     new = repo[n]
     return new, [(oldctx.node(), (n,))]
 
 
 def edit(ui, repo, ctx, ha, opts):
     oldctx = repo[ha]
     hg.update(repo, ctx.node())
     applychanges(ui, repo, oldctx, opts)
     raise error.InterventionRequired(
         _('Make changes as needed, you may commit or record as needed now.\n'
           'When you are finished, run hg histedit --continue to resume.'))
 
 def fold(ui, repo, ctx, ha, opts):
     oldctx = repo[ha]
     hg.update(repo, ctx.node())
     stats = applychanges(ui, repo, oldctx, opts)
     if stats and stats[3] > 0:
         raise error.InterventionRequired(
             _('Fix up the change and run hg histedit --continue'))
     n = repo.commit(text='fold-temp-revision %s' % ha, user=oldctx.user(),
                     date=oldctx.date(), extra=oldctx.extra())
     if n is None:
         ui.warn(_('%s: empty changeset')
                      % node.hex(ha))
         return ctx, []
     return finishfold(ui, repo, ctx, oldctx, n, opts, [])
 
 def finishfold(ui, repo, ctx, oldctx, newnode, opts, internalchanges):
     parent = ctx.parents()[0].node()
     hg.update(repo, parent)
     ### prepare new commit data
     commitopts = opts.copy()
     # username
     if ctx.user() == oldctx.user():
         username = ctx.user()
     else:
         username = ui.username()
     commitopts['user'] = username
     # commit message
     newmessage = '\n***\n'.join(
         [ctx.description()] +
         [repo[r].description() for r in internalchanges] +
         [oldctx.description()]) + '\n'
     commitopts['message'] = newmessage
     # date
     commitopts['date'] = max(ctx.date(), oldctx.date())
     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['histedit_source'] = '%s,%s' % (ctx.hex(), oldctx.hex())
     commitopts['extra'] = extra
     phasebackup = repo.ui.backupconfig('phases', 'new-commit')
     try:
         phasemin = max(ctx.phase(), oldctx.phase())
         repo.ui.setconfig('phases', 'new-commit', phasemin)
         n = collapse(repo, ctx, repo[newnode], commitopts)
     finally:
         repo.ui.restoreconfig(phasebackup)
     if n is None:
         return ctx, []
     hg.update(repo, n)
     replacements = [(oldctx.node(), (newnode,)),
                      (ctx.node(), (n,)),
                      (newnode, (n,)),
                     ]
     for ich in internalchanges:
         replacements.append((ich, (n,)))
     return repo[n], replacements
 
 def drop(ui, repo, ctx, ha, opts):
     return ctx, [(repo[ha].node(), ())]
 
 
 def message(ui, repo, ctx, ha, opts):
     oldctx = repo[ha]
     hg.update(repo, ctx.node())
     stats = applychanges(ui, repo, oldctx, opts)
     if stats and stats[3] > 0:
         raise error.InterventionRequired(
             _('Fix up the change and run hg histedit --continue'))
     message = oldctx.description() + '\n'
     message = ui.edit(message, ui.username())
     commit = commitfuncfor(repo, oldctx)
     new = commit(text=message, user=oldctx.user(), date=oldctx.date(),
                  extra=oldctx.extra())
     newctx = repo[new]
     if oldctx.node() != newctx.node():
         return newctx, [(oldctx.node(), (new,))]
     # We didn't make an edit, so just indicate no replaced nodes
     return newctx, []
 
 def findoutgoing(ui, repo, remote=None, force=False, opts={}):
     """utility function to find the first outgoing changeset
 
     Used by initialisation code"""
     dest = ui.expandpath(remote or 'default-push', remote or 'default')
     dest, revs = hg.parseurl(dest, None)[:2]
     ui.status(_('comparing with %s\n') % util.hidepassword(dest))
 
     revs, checkout = hg.addbranchrevs(repo, repo, revs, None)
     other = hg.peer(repo, opts, dest)
 
     if revs:
         revs = [repo.lookup(rev) for rev in revs]
 
     # hexlify nodes from outgoing, because we're going to parse
     # parent[0] using revsingle below, and if the binary hash
     # contains special revset characters like ":" the revset
     # parser can choke.
     outgoing = discovery.findcommonoutgoing(repo, other, revs, force=force)
     if not outgoing.missing:
         raise util.Abort(_('no outgoing ancestors'))
     return outgoing.missing[0]
 
 actiontable = {'p': pick,
                'pick': pick,
                'e': edit,
                'edit': edit,
                'f': fold,
                'fold': fold,
                'd': drop,
                'drop': drop,
                'm': message,
                'mess': message,
                }
 
 @command('histedit',
     [('', 'commands', '',
       _('Read history edits from the specified file.')),
      ('c', 'continue', False, _('continue an edit already in progress')),
      ('k', 'keep', False,
       _("don't strip old nodes after edit is complete")),
      ('', 'abort', False, _('abort an edit in progress')),
      ('o', 'outgoing', False, _('changesets not found in destination')),
      ('f', 'force', False,
       _('force outgoing even for unrelated repositories')),
      ('r', 'rev', [], _('first revision to be edited'))],
      _("[PARENT]"))
 def histedit(ui, repo, *freeargs, **opts):
     """interactively edit changeset history
     """
     # TODO only abort if we try and histedit mq patches, not just
     # blanket if mq patches are applied somewhere
     mq = getattr(repo, 'mq', None)
     if mq and mq.applied:
         raise util.Abort(_('source has mq patches applied'))
 
     # basic argument incompatibility processing
     outg = opts.get('outgoing')
     cont = opts.get('continue')
     abort = opts.get('abort')
     force = opts.get('force')
     rules = opts.get('commands', '')
     revs = opts.get('rev', [])
     goal = 'new' # This invocation goal, in new, continue, abort
     if force and not outg:
         raise util.Abort(_('--force only allowed with --outgoing'))
     if cont:
         if util.any((outg, abort, revs, freeargs, rules)):
             raise util.Abort(_('no arguments allowed with --continue'))
         goal = 'continue'
     elif abort:
         if util.any((outg, revs, freeargs, rules)):
             raise util.Abort(_('no arguments allowed with --abort'))
         goal = 'abort'
     else:
         if os.path.exists(os.path.join(repo.path, 'histedit-state')):
             raise util.Abort(_('history edit already in progress, try '
                                '--continue or --abort'))
         if outg:
             if revs:
                 raise util.Abort(_('no revisions allowed with --outgoing'))
             if len(freeargs) > 1:
                 raise util.Abort(
                     _('only one repo argument allowed with --outgoing'))
         else:
             revs.extend(freeargs)
             if len(revs) != 1:
                 raise util.Abort(
                     _('histedit requires exactly one parent revision'))
 
 
     if goal == 'continue':
         (parentctxnode, rules, keep, topmost, replacements) = readstate(repo)
         currentparent, wantnull = repo.dirstate.parents()
         parentctx = repo[parentctxnode]
         parentctx, repl = bootstrapcontinue(ui, repo, parentctx, rules, opts)
         replacements.extend(repl)
     elif goal == 'abort':
         (parentctxnode, rules, keep, topmost, replacements) = readstate(repo)
         mapping, tmpnodes, leafs, _ntm = processreplacement(repo, replacements)
         ui.debug('restore wc to old parent %s\n' % node.short(topmost))
         hg.clean(repo, topmost)
         cleanupnode(ui, repo, 'created', tmpnodes)
         cleanupnode(ui, repo, 'temp', leafs)
         os.unlink(os.path.join(repo.path, 'histedit-state'))
         return
     else:
         cmdutil.bailifchanged(repo)
 
         topmost, empty = repo.dirstate.parents()
         if outg:
             if freeargs:
                 remote = freeargs[0]
             else:
                 remote = None
             root = findoutgoing(ui, repo, remote, force, opts)
         else:
             root = revs[0]
             root = scmutil.revsingle(repo, root).node()
 
         keep = opts.get('keep', False)
         revs = between(repo, root, topmost, keep)
         if not revs:
             raise util.Abort(_('%s is not an ancestor of working directory') %
                              node.short(root))
 
         ctxs = [repo[r] for r in revs]
         if not rules:
             rules = '\n'.join([makedesc(c) for c in ctxs])
             rules += '\n\n'
             rules += editcomment % (node.short(root), node.short(topmost))
             rules = ui.edit(rules, ui.username())
             # Save edit rules in .hg/histedit-last-edit.txt in case
             # the user needs to ask for help after something
             # surprising happens.
             f = open(repo.join('histedit-last-edit.txt'), 'w')
             f.write(rules)
             f.close()
         else:
             if rules == '-':
                 f = sys.stdin
             else:
                 f = open(rules)
             rules = f.read()
             f.close()
         rules = [l for l in (r.strip() for r in rules.splitlines())
                  if l and not l[0] == '#']
         rules = verifyrules(rules, repo, ctxs)
 
         parentctx = repo[root].parents()[0]
         keep = opts.get('keep', False)
         replacements = []
 
 
     while rules:
         writestate(repo, parentctx.node(), rules, keep, topmost, replacements)
         action, ha = rules.pop(0)
         ui.debug('histedit: processing %s %s\n' % (action, ha))
         actfunc = actiontable[action]
         parentctx, replacement_ = actfunc(ui, repo, parentctx, ha, opts)
         replacements.extend(replacement_)
 
     hg.update(repo, parentctx.node())
 
     mapping, tmpnodes, created, ntm = processreplacement(repo, replacements)
     if mapping:
         for prec, succs in mapping.iteritems():
             if not succs:
                 ui.debug('histedit: %s is dropped\n' % node.short(prec))
             else:
                 ui.debug('histedit: %s is replaced by %s\n' % (
                     node.short(prec), node.short(succs[0])))
                 if len(succs) > 1:
                     m = 'histedit:                            %s'
                     for n in succs[1:]:
                         ui.debug(m % node.short(n))
 
     if not keep:
         if mapping:
             movebookmarks(ui, repo, mapping, topmost, ntm)
             # TODO update mq state
         if obsolete._enabled:
             markers = []
             # sort by revision number because it sound "right"
             for prec in sorted(mapping, key=repo.changelog.rev):
                 succs = mapping[prec]
                 markers.append((repo[prec],
                                 tuple(repo[s] for s in succs)))
             if markers:
                 obsolete.createmarkers(repo, markers)
         else:
             cleanupnode(ui, repo, 'replaced', mapping)
 
     cleanupnode(ui, repo, 'temp', tmpnodes)
     os.unlink(os.path.join(repo.path, 'histedit-state'))
     if os.path.exists(repo.sjoin('undo')):
         os.unlink(repo.sjoin('undo'))
 
 
 def bootstrapcontinue(ui, repo, parentctx, rules, opts):
     action, currentnode = rules.pop(0)
     ctx = repo[currentnode]
     # is there any new commit between the expected parent and "."
     #
     # note: does not take non linear new change in account (but previous
     #       implementation didn't used them anyway (issue3655)
     newchildren = [c.node() for c in repo.set('(%d::.)', parentctx)]
     if parentctx.node() != node.nullid:
         if not newchildren:
             # `parentctxnode` should match but no result. This means that
             # currentnode is not a descendant from parentctxnode.
             msg = _('%s is not an ancestor of working directory')
             hint = _('update to %s or descendant and run "hg histedit '
                      '--continue" again') % parentctx
             raise util.Abort(msg % parentctx, hint=hint)
         newchildren.pop(0)  # remove parentctxnode
     # Commit dirty working directory if necessary
     new = None
     m, a, r, d = repo.status()[:4]
     if m or a or r or d:
         # prepare the message for the commit to comes
         if action in ('f', 'fold'):
             message = 'fold-temp-revision %s' % currentnode
         else:
             message = ctx.description() + '\n'
         if action in ('e', 'edit', 'm', 'mess'):
             editor = cmdutil.commitforceeditor
         else:
             editor = False
         commit = commitfuncfor(repo, ctx)
         new = commit(text=message, user=ctx.user(),
                      date=ctx.date(), extra=ctx.extra(),
                      editor=editor)
         if new is not None:
             newchildren.append(new)
 
     replacements = []
     # track replacements
     if ctx.node() not in newchildren:
         # note: new children may be empty when the changeset is dropped.
         # this happen e.g during conflicting pick where we revert content
         # to parent.
         replacements.append((ctx.node(), tuple(newchildren)))
 
     if action in ('f', 'fold'):
         if newchildren:
             # finalize fold operation if applicable
             if new is None:
                 new = newchildren[-1]
             else:
                 newchildren.pop()  # remove new from internal changes
             parentctx, repl = finishfold(ui, repo, parentctx, ctx, new, opts,
                                          newchildren)
             replacements.extend(repl)
         else:
             # newchildren is empty if the fold did not result in any commit
             # this happen when all folded change are discarded during the
             # merge.
             replacements.append((ctx.node(), (parentctx.node(),)))
     elif newchildren:
         # otherwise update "parentctx" before proceeding to further operation
         parentctx = repo[newchildren[-1]]
     return parentctx, replacements
 
 
 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."""
     ctxs = list(repo.set('%n::%n', old, new))
     if ctxs and not keep:
         if (not obsolete._enabled and
             repo.revs('(%ld::) - (%ld)', ctxs, ctxs)):
             raise util.Abort(_('cannot edit history that would orphan nodes'))
         root = ctxs[0] # list is already sorted by repo.set
         if not root.phase():
             raise util.Abort(_('cannot edit immutable changeset: %s') % root)
     return [c.node() for c in ctxs]
 
 
 def writestate(repo, parentnode, rules, keep, topmost, replacements):
     fp = open(os.path.join(repo.path, 'histedit-state'), 'w')
     pickle.dump((parentnode, rules, keep, topmost, replacements), fp)
     fp.close()
 
 def readstate(repo):
     """Returns a tuple of (parentnode, rules, keep, topmost, replacements).
     """
     fp = open(os.path.join(repo.path, 'histedit-state'))
     return pickle.load(fp)
 
 
 def makedesc(c):
     """build a initial action line for a ctx `c`
 
     line are in the form:
 
       pick <hash> <rev> <summary>
     """
     summary = ''
     if c.description():
         summary = c.description().splitlines()[0]
     line = 'pick %s %d %s' % (c, c.rev(), summary)
     return line[:80]  # trim to 80 chars so it's not stupidly wide in my editor
 
 def verifyrules(rules, repo, ctxs):
     """Verify that there exists exactly one edit rule per given changeset.
 
     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.
     """
     parsed = []
     expected = set(str(c) for c in ctxs)
     seen = set()
-    if len(rules) != len(expected):
-        raise util.Abort(_('must specify a rule for each changeset once'))
     for r in rules:
         if ' ' not in r:
             raise util.Abort(_('malformed line "%s"') % r)
         action, rest = r.split(' ', 1)
         ha = rest.strip().split(' ', 1)[0]
         try:
             ha = str(repo[ha])  # ensure its a short hash
         except error.RepoError:
             raise util.Abort(_('unknown changeset %s listed') % ha)
         if ha not in expected:
             raise util.Abort(
                 _('may not use changesets other than the ones listed'))
         if ha in seen:
             raise util.Abort(_('duplicated command for changeset %s') % ha)
         seen.add(ha)
         if action not in actiontable:
             raise util.Abort(_('unknown action "%s"') % action)
         parsed.append([action, ha])
+    missing = sorted(expected - seen)  # sort to stabilize output
+    if missing:
+        raise util.Abort(_('missing rules for changeset %s') % missing[0],
+                         hint=_('do you want to use the drop action?'))
     return parsed
 
 def processreplacement(repo, replacements):
     """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"""
     allsuccs = set()
     replaced = set()
     fullmapping = {}
     # initialise basic set
     # fullmapping record all operation 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)
     nm = repo.changelog.nodemap
     for prec, succs in final.items():
         final[prec] = sorted(succs, key=nm.get)
 
     # computed topmost element (necessary for bookmark)
     if new:
         newtopmost = sorted(new, key=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.
         newtopmost = repo[sorted(final, key=repo.changelog.rev)[0]].p1().node()
 
     return final, tmpnodes, new, newtopmost
 
 def movebookmarks(ui, repo, mapping, oldtopmost, newtopmost):
     """Move bookmark from old to newly created node"""
     if not mapping:
         # if nothing got rewritten there is not purpose for this function
         return
     moves = []
     for bk, old in sorted(repo._bookmarks.iteritems()):
         if old == oldtopmost:
             # special case ensure bookmark stay on tip.
             #
             # 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.
             moves.append((bk, newtopmost))
             continue
         base = old
         new = mapping.get(base, None)
         if new is None:
             continue
         while not new:
             # base is killed, trying with parent
             base = repo[base].p1().node()
             new = mapping.get(base, (base,))
             # nothing to move
         moves.append((bk, new[-1]))
     if moves:
         marks = repo._bookmarks
         for mark, new in moves:
             old = marks[mark]
             ui.note(_('histedit: moving bookmarks %s from %s to %s\n')
                     % (mark, node.short(old), node.short(new)))
             marks[mark] = new
         marks.write()
 
 def cleanupnode(ui, repo, name, nodes):
     """strip a group of nodes from the repository
 
     The set of node to strip may contains unknown nodes."""
     ui.debug('should strip %s nodes %s\n' %
              (name, ', '.join([node.short(n) for n in nodes])))
     lock = None
     try:
         lock = repo.lock()
         # Find all node that need to be stripped
         # (we hg %lr instead of %ln to silently ignore unknown item
         nm = repo.changelog.nodemap
         nodes = [n for n in nodes if n in nm]
         roots = [c.node() for c in repo.set("roots(%ln)", nodes)]
         for c in roots:
             # We should process node in reverse order to strip tip most first.
             # but this trigger a bug in changegroup hook.
             # This would reduce bundle overhead
             repair.strip(ui, repo, c)
     finally:
         lockmod.release(lock)

tests/test-histedit-arguments.t

@@ -1,168 +1,169 b''
 Test argument handling and various data parsing
 ==================================================
 
 
 Enable extensions used by this test.
   $ cat >>$HGRCPATH <<EOF
   > [extensions]
   > histedit=
   > EOF
 
 Repo setup.
   $ hg init foo
   $ cd foo
   $ echo alpha >> alpha
   $ hg addr
   adding alpha
   $ hg ci -m one
   $ echo alpha >> alpha
   $ hg ci -m two
   $ echo alpha >> alpha
   $ hg ci -m three
   $ echo alpha >> alpha
   $ hg ci -m four
   $ echo alpha >> alpha
   $ hg ci -m five
 
   $ hg log --style compact --graph
   @  4[tip]   08d98a8350f3   1970-01-01 00:00 +0000   test
   |    five
   |
   o  3   c8e68270e35a   1970-01-01 00:00 +0000   test
   |    four
   |
   o  2   eb57da33312f   1970-01-01 00:00 +0000   test
   |    three
   |
   o  1   579e40513370   1970-01-01 00:00 +0000   test
   |    two
   |
   o  0   6058cbb6cfd7   1970-01-01 00:00 +0000   test
        one
   
 
 Run a dummy edit to make sure we get tip^^ correctly via revsingle.
 --------------------------------------------------------------------
 
   $ HGEDITOR=cat hg histedit "tip^^"
   pick eb57da33312f 2 three
   pick c8e68270e35a 3 four
   pick 08d98a8350f3 4 five
   
   # Edit history between eb57da33312f and 08d98a8350f3
   #
   # Commands:
   #  p, pick = use commit
   #  e, edit = use commit, but stop for amending
   #  f, fold = use commit, but fold into previous commit (combines N and N-1)
   #  d, drop = remove commit from history
   #  m, mess = edit message without changing commit content
   #
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
 Run on a revision not ancestors of the current working directory.
 --------------------------------------------------------------------
 
   $ hg up 2
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg histedit -r 4
   abort: 08d98a8350f3 is not an ancestor of working directory
   [255]
   $ hg up --quiet
 
 Test that missing revisions are detected
 ---------------------------------------
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > pick eb57da33312f 2 three
   > pick 08d98a8350f3 4 five
   > EOF
-  abort: must specify a rule for each changeset once
+  abort: missing rules for changeset c8e68270e35a
+  (do you want to use the drop action?)
   [255]
 
 Test that extra revisions are detected
 ---------------------------------------
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > pick 6058cbb6cfd7 0 one
   > pick c8e68270e35a 3 four
   > pick 08d98a8350f3 4 five
   > EOF
   abort: may not use changesets other than the ones listed
   [255]
 
 Test malformed line
 ---------------------------------------
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > pickeb57da33312f2three
   > pick c8e68270e35a 3 four
   > pick 08d98a8350f3 4 five
   > EOF
   abort: malformed line "pickeb57da33312f2three"
   [255]
 
 Test unknown changeset
 ---------------------------------------
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > pick 0123456789ab 2 three
   > pick c8e68270e35a 3 four
   > pick 08d98a8350f3 4 five
   > EOF
   abort: unknown changeset 0123456789ab listed
   [255]
 
 Test unknown command
 ---------------------------------------
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > coin eb57da33312f 2 three
   > pick c8e68270e35a 3 four
   > pick 08d98a8350f3 4 five
   > EOF
   abort: unknown action "coin"
   [255]
 
 Test duplicated changeset
 ---------------------------------------
 
 So one is missing and one appear twice.
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > pick eb57da33312f 2 three
   > pick eb57da33312f 2 three
   > pick 08d98a8350f3 4 five
   > EOF
   abort: duplicated command for changeset eb57da33312f
   [255]
 
 Test short version of command
 ---------------------------------------
 
 Note: we use varying amounts of white space between command name and changeset
 short hash. This tests issue3893.
 
   $ HGEDITOR=cat hg histedit "tip^^" --commands - << EOF
   > pick eb57da33312f 2 three
   > p    c8e68270e35a 3 four
   > f 08d98a8350f3 4 five
   > EOF
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   reverting alpha
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   four
   ***
   five
   
   
   
   HG: Enter commit message.  Lines beginning with 'HG:' are removed.
   HG: Leave message empty to abort commit.
   HG: --
   HG: user: test
   HG: branch 'default'
   HG: changed alpha
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   saved backup bundle to $TESTTMP/foo/.hg/strip-backup/*-backup.hg (glob)