rebase: calculate ancestors for --base separately (issue5420)

Previously, the --base option only works with a single "branch" - if there
is one changeset in the "--base" revset whose branching point(s) is/are
different from another changeset in the "--base" revset, "rebase" will error
out with:

  abort: source is ancestor of destination

This happens if the user has multiple draft branches, and uses "hg rebase -b
'draft()' -d master", for example. The error message looks cryptic to users
who don't know the implementation detail.

This patch changes the logic to calculate the common ancestor for every
"base" changeset separately so we won't (incorrectly) select "source" which
is an ancestor of the destination.

This patch should not change the behavior where all changesets specified by
"--base" have the same branching point(s).

A new situation is: some of the specified changesets could be rebased, while
some couldn't (because they are descendants of the destination, or they do
not share a common ancestor with the destination). The current behavior is
to show "nothing to rebase" and exits with 1.

This patch maintains the current behavior (show "nothing to rebase") even if
part of the "--base" revset could be rebased. A clearer error message may be
"cannot find branching point for X", or "X is a descendant of destination".
The error message issue is tracked by issue5422 separately.

A test is added with all kinds of tricky cases I could think of for now.

tests/test-rebase-base.t

@@ -0,0 +1,393 b''
+  $ cat >> $HGRCPATH <<EOF
+  > [extensions]
+  > rebase=
+  > drawdag=$TESTDIR/drawdag.py
+  > 
+  > [phases]
+  > publish=False
+  > 
+  > [alias]
+  > tglog = log -G --template "{rev}: {desc}"
+  > EOF
+
+  $ rebasewithdag() {
+  >   N=`$PYTHON -c "print($N+1)"`
+  >   hg init repo$N && cd repo$N
+  >   hg debugdrawdag
+  >   hg rebase "$@" > _rebasetmp
+  >   r=$?
+  >   grep -v 'saved backup bundle' _rebasetmp
+  >   [ $r -eq 0 ] && hg tglog
+  >   cd ..
+  >   return $r
+  > }
+
+Single branching point, without merge:
+
+  $ rebasewithdag -b D -d Z <<'EOS'
+  >     D E
+  >     |/
+  > Z B C   # C: branching point, E should be picked
+  >  \|/    # B should not be picked
+  >   A
+  >   |
+  >   R
+  > EOS
+  rebasing 3:d6003a550c2c "C" (C)
+  rebasing 5:4526cf523425 "D" (D)
+  rebasing 6:b296604d9846 "E" (E tip)
+  o  6: E
+  |
+  | o  5: D
+  |/
+  o  4: C
+  |
+  o  3: Z
+  |
+  | o  2: B
+  |/
+  o  1: A
+  |
+  o  0: R
+  
+Multiple branching points caused by selecting a single merge changeset:
+
+  $ rebasewithdag -b E -d Z <<'EOS'
+  >     E
+  >    /|
+  >   B C D  # B, C: multiple branching points
+  >   | |/   # D should not be picked
+  > Z | /
+  >  \|/
+  >   A
+  >   |
+  >   R
+  > EOS
+  rebasing 2:c1e6b162678d "B" (B)
+  rebasing 3:d6003a550c2c "C" (C)
+  rebasing 6:5251e0cb7302 "E" (E tip)
+  o    6: E
+  |\
+  | o  5: C
+  | |
+  o |  4: B
+  |/
+  o  3: Z
+  |
+  | o  2: D
+  |/
+  o  1: A
+  |
+  o  0: R
+  
+Rebase should not extend the "--base" revset using "descendants":
+
+  $ rebasewithdag -b B -d Z <<'EOS'
+  >     E
+  >    /|
+  > Z B C  # descendants(B) = B+E. With E, C will be included incorrectly
+  >  \|/
+  >   A
+  >   |
+  >   R
+  > EOS
+  rebasing 2:c1e6b162678d "B" (B)
+  rebasing 5:5251e0cb7302 "E" (E tip)
+  o    5: E
+  |\
+  | o  4: B
+  | |
+  | o  3: Z
+  | |
+  o |  2: C
+  |/
+  o  1: A
+  |
+  o  0: R
+  
+Rebase should not simplify the "--base" revset using "roots":
+
+  $ rebasewithdag -b B+E -d Z <<'EOS'
+  >     E
+  >    /|
+  > Z B C  # roots(B+E) = B. Without E, C will be missed incorrectly
+  >  \|/
+  >   A
+  >   |
+  >   R
+  > EOS
+  rebasing 2:c1e6b162678d "B" (B)
+  rebasing 3:d6003a550c2c "C" (C)
+  rebasing 5:5251e0cb7302 "E" (E tip)
+  o    5: E
+  |\
+  | o  4: C
+  | |
+  o |  3: B
+  |/
+  o  2: Z
+  |
+  o  1: A
+  |
+  o  0: R
+  
+The destination is one of the two branching points of a merge:
+
+  $ rebasewithdag -b F -d Z <<'EOS'
+  >     F
+  >    / \
+  >   E   D
+  >  /   /
+  > Z   C
+  >  \ /
+  >   B
+  >   |
+  >   A
+  > EOS
+  nothing to rebase
+  [1]
+
+Multiple branching points caused by multiple bases (issue5420):
+
+  $ rebasewithdag -b E1+E2+C2+B1 -d Z <<'EOS'
+  >   Z    E2
+  >   |   /
+  >   F E1 C2
+  >   |/  /
+  >   E C1 B2
+  >   |/  /
+  >   C B1
+  >   |/
+  >   B
+  >   |
+  >   A
+  >   |
+  >   R
+  > EOS
+  rebasing 3:a113dbaa660a "B1" (B1)
+  rebasing 5:06ce7b1cc8c2 "B2" (B2)
+  rebasing 6:0ac98cce32d3 "C1" (C1)
+  rebasing 8:781512f5e33d "C2" (C2)
+  rebasing 9:428d8c18f641 "E1" (E1)
+  rebasing 11:e1bf82f6b6df "E2" (E2)
+  o  12: E2
+  |
+  o  11: E1
+  |
+  | o  10: C2
+  | |
+  | o  9: C1
+  |/
+  | o  8: B2
+  | |
+  | o  7: B1
+  |/
+  o  6: Z
+  |
+  o  5: F
+  |
+  o  4: E
+  |
+  o  3: C
+  |
+  o  2: B
+  |
+  o  1: A
+  |
+  o  0: R
+  
+Multiple branching points with multiple merges:
+
+  $ rebasewithdag -b G+P -d Z <<'EOS'
+  > G   H   P
+  > |\ /|   |\
+  > F E D   M N
+  >  \|/|  /| |\
+  > Z C B I J K L
+  >  \|/  |/  |/
+  >   A   A   A
+  > EOS
+  rebasing 2:dc0947a82db8 "C" (C)
+  rebasing 8:215e7b0814e1 "D" (D)
+  rebasing 9:03ca77807e91 "E" (E)
+  rebasing 10:afc707c82df0 "F" (F)
+  rebasing 13:018caa673317 "G" (G)
+  rebasing 14:4f710fbd68cb "H" (H)
+  rebasing 3:08ebfeb61bac "I" (I)
+  rebasing 4:a0a5005cec67 "J" (J)
+  rebasing 5:83780307a7e8 "K" (K)
+  rebasing 6:e131637a1cb6 "L" (L)
+  rebasing 11:d6fe3d11d95d "M" (M)
+  rebasing 12:fa1e02269063 "N" (N)
+  rebasing 15:448b1a498430 "P" (P tip)
+  o    15: P
+  |\
+  | o    14: N
+  | |\
+  o \ \    13: M
+  |\ \ \
+  | | | o  12: L
+  | | | |
+  | | o |  11: K
+  | | |/
+  | o /  10: J
+  | |/
+  o /  9: I
+  |/
+  | o    8: H
+  | |\
+  | | | o  7: G
+  | | |/|
+  | | | o  6: F
+  | | | |
+  | | o |  5: E
+  | | |/
+  | o |  4: D
+  | |\|
+  +---o  3: C
+  | |
+  o |  2: Z
+  | |
+  | o  1: B
+  |/
+  o  0: A
+  
+Slightly more complex merge case (mentioned in https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-November/091074.html):
+
+  $ rebasewithdag -b A3+B3 -d Z <<'EOF'
+  > Z     C1    A3     B3
+  > |    /     / \    / \
+  > M3 C0     A1  A2 B1  B2
+  > | /       |   |  |   |
+  > M2        M1  C1 C1  M3
+  > |
+  > M1
+  > |
+  > M0
+  > EOF
+  rebasing 4:8817fae53c94 "C0" (C0)
+  rebasing 6:06ca5dfe3b5b "B2" (B2)
+  rebasing 7:73508237b032 "C1" (C1)
+  rebasing 9:fdb955e2faed "A2" (A2)
+  rebasing 11:1b2f368c3cb5 "A3" (A3)
+  rebasing 10:0a33b0519128 "B1" (B1)
+  rebasing 12:bd6a37b5b67a "B3" (B3 tip)
+  o    12: B3
+  |\
+  | o  11: B1
+  | |
+  | | o    10: A3
+  | | |\
+  | +---o  9: A2
+  | | |
+  | o |  8: C1
+  | | |
+  o | |  7: B2
+  | | |
+  | o |  6: C0
+  |/ /
+  o |  5: Z
+  | |
+  o |  4: M3
+  | |
+  o |  3: M2
+  | |
+  | o  2: A1
+  |/
+  o  1: M1
+  |
+  o  0: M0
+  
+Mixed rebasable and non-rebasable bases (unresolved, issue5422):
+
+  $ rebasewithdag -b C+D -d B <<'EOS'
+  >   D
+  >  /
+  > B C
+  > |/
+  > A
+  > EOS
+  nothing to rebase
+  [1]
+
+Disconnected graph:
+
+  $ rebasewithdag -b B -d Z <<'EOS'
+  >   B
+  >   |
+  > Z A
+  > EOS
+  nothing to rebase from 112478962961 to 48b9aae0607f
+  [1]
+
+Multiple roots. Roots are ancestors of dest:
+
+  $ rebasewithdag -b B+D -d Z <<'EOF'
+  > D Z B
+  >  \|\|
+  >   C A
+  > EOF
+  rebasing 2:112478962961 "B" (B)
+  rebasing 3:b70f76719894 "D" (D)
+  o  4: D
+  |
+  | o  3: B
+  |/
+  o    2: Z
+  |\
+  | o  1: C
+  |
+  o  0: A
+  
+Multiple roots. One root is not an ancestor of dest:
+
+  $ rebasewithdag -b B+D -d Z <<'EOF'
+  > Z B D
+  >  \|\|
+  >   A C
+  > EOF
+  nothing to rebase from 86d01f49c0d9+b70f76719894 to 262e37e34f63
+  [1]
+
+Multiple roots. One root is not an ancestor of dest. Select using a merge:
+
+  $ rebasewithdag -b E -d Z <<'EOF'
+  >   E
+  >   |\
+  > Z B D
+  >  \|\|
+  >   A C
+  > EOF
+  rebasing 2:86d01f49c0d9 "B" (B)
+  rebasing 5:539a0ff83ea9 "E" (E tip)
+  o    5: E
+  |\
+  | o    4: B
+  | |\
+  | | o  3: Z
+  | | |
+  o | |  2: D
+  |/ /
+  o /  1: C
+   /
+  o  0: A
+  
+Multiple roots. Two children share two parents while dest has only one parent:
+
+  $ rebasewithdag -b B+D -d Z <<'EOF'
+  > Z B D
+  >  \|\|\
+  >   A C A
+  > EOF
+  rebasing 2:86d01f49c0d9 "B" (B)
+  rebasing 3:b7df2ca01aa8 "D" (D)
+  o    4: D
+  |\
+  +---o  3: B
+  | |/
+  | o  2: Z
+  | |
+  o |  1: C
+   /
+  o  0: A
+  

hgext/rebase.py

@@ -1,1455 +1,1462 b''
 # rebase.py - rebasing feature for mercurial
 #
 # Copyright 2008 Stefano Tortarolo <stefano.tortarolo at gmail dot com>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 '''command to move sets of revisions to a different ancestor
 
 This extension lets you rebase changesets in an existing Mercurial
 repository.
 
 For more information:
 https://mercurial-scm.org/wiki/RebaseExtension
 '''
 
 from __future__ import absolute_import
 
 import errno
 import os
 
 from mercurial.i18n import _
 from mercurial.node import (
     hex,
     nullid,
     nullrev,
     short,
 )
 from mercurial import (
     bookmarks,
     cmdutil,
     commands,
     copies,
     destutil,
     dirstateguard,
     error,
     extensions,
     hg,
     lock,
     merge as mergemod,
     mergeutil,
     obsolete,
     patch,
     phases,
     registrar,
     repair,
     repoview,
     revset,
     scmutil,
     util,
 )
 
 release = lock.release
 templateopts = commands.templateopts
 
 # The following constants are used throughout the rebase module. The ordering of
 # their values must be maintained.
 
 # Indicates that a revision needs to be rebased
 revtodo = -1
 nullmerge = -2
 revignored = -3
 # successor in rebase destination
 revprecursor = -4
 # plain prune (no successor)
 revpruned = -5
 revskipped = (revignored, revprecursor, revpruned)
 
 cmdtable = {}
 command = cmdutil.command(cmdtable)
 # 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 = 'ships-with-hg-core'
 
 def _nothingtorebase():
     return 1
 
 def _savegraft(ctx, extra):
     s = ctx.extra().get('source', None)
     if s is not None:
         extra['source'] = s
     s = ctx.extra().get('intermediate-source', None)
     if s is not None:
         extra['intermediate-source'] = s
 
 def _savebranch(ctx, extra):
     extra['branch'] = ctx.branch()
 
 def _makeextrafn(copiers):
     """make an extrafn out of the given copy-functions.
 
     A copy function takes a context and an extra dict, and mutates the
     extra dict as needed based on the given context.
     """
     def extrafn(ctx, extra):
         for c in copiers:
             c(ctx, extra)
     return extrafn
 
 def _destrebase(repo, sourceset, destspace=None):
     """small wrapper around destmerge to pass the right extra args
 
     Please wrap destutil.destmerge instead."""
     return destutil.destmerge(repo, action='rebase', sourceset=sourceset,
                               onheadcheck=False, destspace=destspace)
 
 revsetpredicate = registrar.revsetpredicate()
 
 @revsetpredicate('_destrebase')
 def _revsetdestrebase(repo, subset, x):
     # ``_rebasedefaultdest()``
 
     # default destination for rebase.
     # # XXX: Currently private because I expect the signature to change.
     # # XXX: - bailing out in case of ambiguity vs returning all data.
     # i18n: "_rebasedefaultdest" is a keyword
     sourceset = None
     if x is not None:
         sourceset = revset.getset(repo, revset.fullreposet(repo), x)
     return subset & revset.baseset([_destrebase(repo, sourceset)])
 
 class rebaseruntime(object):
     """This class is a container for rebase runtime state"""
     def __init__(self, repo, ui, opts=None):
         if opts is None:
             opts = {}
 
         self.repo = repo
         self.ui = ui
         self.opts = opts
         self.originalwd = None
         self.external = nullrev
         # Mapping between the old revision id and either what is the new rebased
         # revision or what needs to be done with the old revision. The state
         # dict will be what contains most of the rebase progress state.
         self.state = {}
         self.activebookmark = None
         self.currentbookmarks = None
         self.target = None
         self.skipped = set()
         self.targetancestors = set()
 
         self.collapsef = opts.get('collapse', False)
         self.collapsemsg = cmdutil.logmessage(ui, opts)
         self.date = opts.get('date', None)
 
         e = opts.get('extrafn') # internal, used by e.g. hgsubversion
         self.extrafns = [_savegraft]
         if e:
             self.extrafns = [e]
 
         self.keepf = opts.get('keep', False)
         self.keepbranchesf = opts.get('keepbranches', False)
         # keepopen is not meant for use on the command line, but by
         # other extensions
         self.keepopen = opts.get('keepopen', False)
         self.obsoletenotrebased = {}
 
     def restorestatus(self):
         """Restore a previously stored status"""
         repo = self.repo
         keepbranches = None
         target = None
         collapse = False
         external = nullrev
         activebookmark = None
         state = {}
 
         try:
             f = repo.vfs("rebasestate")
             for i, l in enumerate(f.read().splitlines()):
                 if i == 0:
                     originalwd = repo[l].rev()
                 elif i == 1:
                     target = repo[l].rev()
                 elif i == 2:
                     external = repo[l].rev()
                 elif i == 3:
                     collapse = bool(int(l))
                 elif i == 4:
                     keep = bool(int(l))
                 elif i == 5:
                     keepbranches = bool(int(l))
                 elif i == 6 and not (len(l) == 81 and ':' in l):
                     # line 6 is a recent addition, so for backwards
                     # compatibility check that the line doesn't look like the
                     # oldrev:newrev lines
                     activebookmark = l
                 else:
                     oldrev, newrev = l.split(':')
                     if newrev in (str(nullmerge), str(revignored),
                                   str(revprecursor), str(revpruned)):
                         state[repo[oldrev].rev()] = int(newrev)
                     elif newrev == nullid:
                         state[repo[oldrev].rev()] = revtodo
                         # Legacy compat special case
                     else:
                         state[repo[oldrev].rev()] = repo[newrev].rev()
 
         except IOError as err:
             if err.errno != errno.ENOENT:
                 raise
             cmdutil.wrongtooltocontinue(repo, _('rebase'))
 
         if keepbranches is None:
             raise error.Abort(_('.hg/rebasestate is incomplete'))
 
         skipped = set()
         # recompute the set of skipped revs
         if not collapse:
             seen = set([target])
             for old, new in sorted(state.items()):
                 if new != revtodo and new in seen:
                     skipped.add(old)
                 seen.add(new)
         repo.ui.debug('computed skipped revs: %s\n' %
                         (' '.join(str(r) for r in sorted(skipped)) or None))
         repo.ui.debug('rebase status resumed\n')
         _setrebasesetvisibility(repo, state.keys())
 
         self.originalwd = originalwd
         self.target = target
         self.state = state
         self.skipped = skipped
         self.collapsef = collapse
         self.keepf = keep
         self.keepbranchesf = keepbranches
         self.external = external
         self.activebookmark = activebookmark
 
     def _handleskippingobsolete(self, rebaserevs, obsoleterevs, target):
         """Compute structures necessary for skipping obsolete revisions
 
         rebaserevs:     iterable of all revisions that are to be rebased
         obsoleterevs:   iterable of all obsolete revisions in rebaseset
         target:         a destination revision for the rebase operation
         """
         self.obsoletenotrebased = {}
         if not self.ui.configbool('experimental', 'rebaseskipobsolete',
                                   default=True):
             return
         rebaseset = set(rebaserevs)
         obsoleteset = set(obsoleterevs)
         self.obsoletenotrebased = _computeobsoletenotrebased(self.repo,
                                     obsoleteset, target)
         skippedset = set(self.obsoletenotrebased)
         _checkobsrebase(self.repo, self.ui, obsoleteset, rebaseset, skippedset)
 
     def _prepareabortorcontinue(self, isabort):
         try:
             self.restorestatus()
             self.collapsemsg = restorecollapsemsg(self.repo)
         except error.RepoLookupError:
             if isabort:
                 clearstatus(self.repo)
                 clearcollapsemsg(self.repo)
                 self.repo.ui.warn(_('rebase aborted (no revision is removed,'
                                     ' only broken state is cleared)\n'))
                 return 0
             else:
                 msg = _('cannot continue inconsistent rebase')
                 hint = _('use "hg rebase --abort" to clear broken state')
                 raise error.Abort(msg, hint=hint)
         if isabort:
             return abort(self.repo, self.originalwd, self.target,
                          self.state, activebookmark=self.activebookmark)
 
         obsrevs = (r for r, st in self.state.items() if st == revprecursor)
         self._handleskippingobsolete(self.state.keys(), obsrevs, self.target)
 
     def _preparenewrebase(self, dest, rebaseset):
         if dest is None:
             return _nothingtorebase()
 
         allowunstable = obsolete.isenabled(self.repo, obsolete.allowunstableopt)
         if (not (self.keepf or allowunstable)
               and self.repo.revs('first(children(%ld) - %ld)',
                                  rebaseset, rebaseset)):
             raise error.Abort(
                 _("can't remove original changesets with"
                   " unrebased descendants"),
                 hint=_('use --keep to keep original changesets'))
 
         obsrevs = _filterobsoleterevs(self.repo, set(rebaseset))
         self._handleskippingobsolete(rebaseset, obsrevs, dest)
 
         result = buildstate(self.repo, dest, rebaseset, self.collapsef,
                             self.obsoletenotrebased)
 
         if not result:
             # Empty state built, nothing to rebase
             self.ui.status(_('nothing to rebase\n'))
             return _nothingtorebase()
 
         root = min(rebaseset)
         if not self.keepf and not self.repo[root].mutable():
             raise error.Abort(_("can't rebase public changeset %s")
                              % self.repo[root],
                              hint=_("see 'hg help phases' for details"))
 
         (self.originalwd, self.target, self.state) = result
         if self.collapsef:
             self.targetancestors = self.repo.changelog.ancestors(
                                         [self.target],
                                         inclusive=True)
             self.external = externalparent(self.repo, self.state,
                                               self.targetancestors)
 
         if dest.closesbranch() and not self.keepbranchesf:
             self.ui.status(_('reopening closed branch head %s\n') % dest)
 
     def _performrebase(self):
         repo, ui, opts = self.repo, self.ui, self.opts
         if self.keepbranchesf:
             # insert _savebranch at the start of extrafns so if
             # there's a user-provided extrafn it can clobber branch if
             # desired
             self.extrafns.insert(0, _savebranch)
             if self.collapsef:
                 branches = set()
                 for rev in self.state:
                     branches.add(repo[rev].branch())
                     if len(branches) > 1:
                         raise error.Abort(_('cannot collapse multiple named '
                             'branches'))
 
         # Rebase
         if not self.targetancestors:
             self.targetancestors = repo.changelog.ancestors([self.target],
                                                                inclusive=True)
 
         # Keep track of the current bookmarks in order to reset them later
         self.currentbookmarks = repo._bookmarks.copy()
         self.activebookmark = self.activebookmark or repo._activebookmark
         if self.activebookmark:
             bookmarks.deactivate(repo)
 
         sortedrevs = repo.revs('sort(%ld, -topo)', self.state)
         cands = [k for k, v in self.state.iteritems() if v == revtodo]
         total = len(cands)
         pos = 0
         for rev in sortedrevs:
             ctx = repo[rev]
             desc = '%d:%s "%s"' % (ctx.rev(), ctx,
                                    ctx.description().split('\n', 1)[0])
             names = repo.nodetags(ctx.node()) + repo.nodebookmarks(ctx.node())
             if names:
                 desc += ' (%s)' % ' '.join(names)
             if self.state[rev] == revtodo:
                 pos += 1
                 ui.status(_('rebasing %s\n') % desc)
                 ui.progress(_("rebasing"), pos, ("%d:%s" % (rev, ctx)),
                             _('changesets'), total)
                 p1, p2, base = defineparents(repo, rev, self.target,
                                              self.state,
                                              self.targetancestors,
                                              self.obsoletenotrebased)
                 storestatus(repo, self.originalwd, self.target,
                             self.state, self.collapsef, self.keepf,
                             self.keepbranchesf, self.external,
                             self.activebookmark)
                 storecollapsemsg(repo, self.collapsemsg)
                 if len(repo[None].parents()) == 2:
                     repo.ui.debug('resuming interrupted rebase\n')
                 else:
                     try:
                         ui.setconfig('ui', 'forcemerge', opts.get('tool', ''),
                                      'rebase')
                         stats = rebasenode(repo, rev, p1, base, self.state,
                                            self.collapsef, self.target)
                         if stats and stats[3] > 0:
                             raise error.InterventionRequired(
                                 _('unresolved conflicts (see hg '
                                   'resolve, then hg rebase --continue)'))
                     finally:
                         ui.setconfig('ui', 'forcemerge', '', 'rebase')
                 if not self.collapsef:
                     merging = p2 != nullrev
                     editform = cmdutil.mergeeditform(merging, 'rebase')
                     editor = cmdutil.getcommiteditor(editform=editform, **opts)
                     newnode = concludenode(repo, rev, p1, p2,
                                            extrafn=_makeextrafn(self.extrafns),
                                            editor=editor,
                                            keepbranches=self.keepbranchesf,
                                            date=self.date)
                 else:
                     # Skip commit if we are collapsing
                     repo.dirstate.beginparentchange()
                     repo.setparents(repo[p1].node())
                     repo.dirstate.endparentchange()
                     newnode = None
                 # Update the state
                 if newnode is not None:
                     self.state[rev] = repo[newnode].rev()
                     ui.debug('rebased as %s\n' % short(newnode))
                 else:
                     if not self.collapsef:
                         ui.warn(_('note: rebase of %d:%s created no changes '
                                   'to commit\n') % (rev, ctx))
                         self.skipped.add(rev)
                     self.state[rev] = p1
                     ui.debug('next revision set to %s\n' % p1)
             elif self.state[rev] == nullmerge:
                 ui.debug('ignoring null merge rebase of %s\n' % rev)
             elif self.state[rev] == revignored:
                 ui.status(_('not rebasing ignored %s\n') % desc)
             elif self.state[rev] == revprecursor:
                 targetctx = repo[self.obsoletenotrebased[rev]]
                 desctarget = '%d:%s "%s"' % (targetctx.rev(), targetctx,
                              targetctx.description().split('\n', 1)[0])
                 msg = _('note: not rebasing %s, already in destination as %s\n')
                 ui.status(msg % (desc, desctarget))
             elif self.state[rev] == revpruned:
                 msg = _('note: not rebasing %s, it has no successor\n')
                 ui.status(msg % desc)
             else:
                 ui.status(_('already rebased %s as %s\n') %
                           (desc, repo[self.state[rev]]))
 
         ui.progress(_('rebasing'), None)
         ui.note(_('rebase merging completed\n'))
 
     def _finishrebase(self):
         repo, ui, opts = self.repo, self.ui, self.opts
         if self.collapsef and not self.keepopen:
             p1, p2, _base = defineparents(repo, min(self.state),
                                           self.target, self.state,
                                           self.targetancestors,
                                           self.obsoletenotrebased)
             editopt = opts.get('edit')
             editform = 'rebase.collapse'
             if self.collapsemsg:
                 commitmsg = self.collapsemsg
             else:
                 commitmsg = 'Collapsed revision'
                 for rebased in self.state:
                     if rebased not in self.skipped and\
                        self.state[rebased] > nullmerge:
                         commitmsg += '\n* %s' % repo[rebased].description()
                 editopt = True
             editor = cmdutil.getcommiteditor(edit=editopt, editform=editform)
             revtoreuse = max(self.state)
             newnode = concludenode(repo, revtoreuse, p1, self.external,
                                    commitmsg=commitmsg,
                                    extrafn=_makeextrafn(self.extrafns),
                                    editor=editor,
                                    keepbranches=self.keepbranchesf,
                                    date=self.date)
             if newnode is None:
                 newrev = self.target
             else:
                 newrev = repo[newnode].rev()
             for oldrev in self.state.iterkeys():
                 if self.state[oldrev] > nullmerge:
                     self.state[oldrev] = newrev
 
         if 'qtip' in repo.tags():
             updatemq(repo, self.state, self.skipped, **opts)
 
         if self.currentbookmarks:
             # Nodeids are needed to reset bookmarks
             nstate = {}
             for k, v in self.state.iteritems():
                 if v > nullmerge:
                     nstate[repo[k].node()] = repo[v].node()
                 elif v == revprecursor:
                     succ = self.obsoletenotrebased[k]
                     nstate[repo[k].node()] = repo[succ].node()
             # XXX this is the same as dest.node() for the non-continue path --
             # this should probably be cleaned up
             targetnode = repo[self.target].node()
 
         # restore original working directory
         # (we do this before stripping)
         newwd = self.state.get(self.originalwd, self.originalwd)
         if newwd == revprecursor:
             newwd = self.obsoletenotrebased[self.originalwd]
         elif newwd < 0:
             # original directory is a parent of rebase set root or ignored
             newwd = self.originalwd
         if newwd not in [c.rev() for c in repo[None].parents()]:
             ui.note(_("update back to initial working directory parent\n"))
             hg.updaterepo(repo, newwd, False)
 
         if self.currentbookmarks:
             with repo.transaction('bookmark') as tr:
                 updatebookmarks(repo, targetnode, nstate,
                                 self.currentbookmarks, tr)
                 if self.activebookmark not in repo._bookmarks:
                     # active bookmark was divergent one and has been deleted
                     self.activebookmark = None
 
         if not self.keepf:
             collapsedas = None
             if self.collapsef:
                 collapsedas = newnode
             clearrebased(ui, repo, self.state, self.skipped, collapsedas)
 
         clearstatus(repo)
         clearcollapsemsg(repo)
 
         ui.note(_("rebase completed\n"))
         util.unlinkpath(repo.sjoin('undo'), ignoremissing=True)
         if self.skipped:
             skippedlen = len(self.skipped)
             ui.note(_("%d revisions have been skipped\n") % skippedlen)
 
         if (self.activebookmark and
             repo['.'].node() == repo._bookmarks[self.activebookmark]):
                 bookmarks.activate(repo, self.activebookmark)
 
 @command('rebase',
     [('s', 'source', '',
      _('rebase the specified changeset and descendants'), _('REV')),
     ('b', 'base', '',
      _('rebase everything from branching point of specified changeset'),
      _('REV')),
     ('r', 'rev', [],
      _('rebase these revisions'),
      _('REV')),
     ('d', 'dest', '',
      _('rebase onto the specified changeset'), _('REV')),
     ('', 'collapse', False, _('collapse the rebased changesets')),
     ('m', 'message', '',
      _('use text as collapse commit message'), _('TEXT')),
     ('e', 'edit', False, _('invoke editor on commit messages')),
     ('l', 'logfile', '',
      _('read collapse commit message from file'), _('FILE')),
     ('k', 'keep', False, _('keep original changesets')),
     ('', 'keepbranches', False, _('keep original branch names')),
     ('D', 'detach', False, _('(DEPRECATED)')),
     ('i', 'interactive', False, _('(DEPRECATED)')),
     ('t', 'tool', '', _('specify merge tool')),
     ('c', 'continue', False, _('continue an interrupted rebase')),
     ('a', 'abort', False, _('abort an interrupted rebase'))] +
      templateopts,
     _('[-s REV | -b REV] [-d REV] [OPTION]'))
 def rebase(ui, repo, **opts):
     """move changeset (and descendants) to a different branch
 
     Rebase uses repeated merging to graft changesets from one part of
     history (the source) onto another (the destination). This can be
     useful for linearizing *local* changes relative to a master
     development tree.
 
     Published commits cannot be rebased (see :hg:`help phases`).
     To copy commits, see :hg:`help graft`.
 
     If you don't specify a destination changeset (``-d/--dest``), rebase
     will use the same logic as :hg:`merge` to pick a destination.  if
     the current branch contains exactly one other head, the other head
     is merged with by default.  Otherwise, an explicit revision with
     which to merge with must be provided.  (destination changeset is not
     modified by rebasing, but new changesets are added as its
     descendants.)
 
     Here are the ways to select changesets:
 
       1. Explicitly select them using ``--rev``.
 
       2. Use ``--source`` to select a root changeset and include all of its
          descendants.
 
       3. Use ``--base`` to select a changeset; rebase will find ancestors
          and their descendants which are not also ancestors of the destination.
 
       4. If you do not specify any of ``--rev``, ``source``, or ``--base``,
          rebase will use ``--base .`` as above.
 
     Rebase will destroy original changesets unless you use ``--keep``.
     It will also move your bookmarks (even if you do).
 
     Some changesets may be dropped if they do not contribute changes
     (e.g. merges from the destination branch).
 
     Unlike ``merge``, rebase will do nothing if you are at the branch tip of
     a named branch with two heads. You will need to explicitly specify source
     and/or destination.
 
     If you need to use a tool to automate merge/conflict decisions, you
     can specify one with ``--tool``, see :hg:`help merge-tools`.
     As a caveat: the tool will not be used to mediate when a file was
     deleted, there is no hook presently available for this.
 
     If a rebase is interrupted to manually resolve a conflict, it can be
     continued with --continue/-c or aborted with --abort/-a.
 
     .. container:: verbose
 
       Examples:
 
       - move "local changes" (current commit back to branching point)
         to the current branch tip after a pull::
 
           hg rebase
 
       - move a single changeset to the stable branch::
 
           hg rebase -r 5f493448 -d stable
 
       - splice a commit and all its descendants onto another part of history::
 
           hg rebase --source c0c3 --dest 4cf9
 
       - rebase everything on a branch marked by a bookmark onto the
         default branch::
 
           hg rebase --base myfeature --dest default
 
       - collapse a sequence of changes into a single commit::
 
           hg rebase --collapse -r 1520:1525 -d .
 
       - move a named branch while preserving its name::
 
           hg rebase -r "branch(featureX)" -d 1.3 --keepbranches
 
     Returns 0 on success, 1 if nothing to rebase or there are
     unresolved conflicts.
 
     """
     rbsrt = rebaseruntime(repo, ui, opts)
 
     lock = wlock = None
     try:
         wlock = repo.wlock()
         lock = repo.lock()
 
         # Validate input and define rebasing points
         destf = opts.get('dest', None)
         srcf = opts.get('source', None)
         basef = opts.get('base', None)
         revf = opts.get('rev', [])
         # search default destination in this space
         # used in the 'hg pull --rebase' case, see issue 5214.
         destspace = opts.get('_destspace')
         contf = opts.get('continue')
         abortf = opts.get('abort')
         if opts.get('interactive'):
             try:
                 if extensions.find('histedit'):
                     enablehistedit = ''
             except KeyError:
                 enablehistedit = " --config extensions.histedit="
             help = "hg%s help -e histedit" % enablehistedit
             msg = _("interactive history editing is supported by the "
                     "'histedit' extension (see \"%s\")") % help
             raise error.Abort(msg)
 
         if rbsrt.collapsemsg and not rbsrt.collapsef:
             raise error.Abort(
                 _('message can only be specified with collapse'))
 
         if contf or abortf:
             if contf and abortf:
                 raise error.Abort(_('cannot use both abort and continue'))
             if rbsrt.collapsef:
                 raise error.Abort(
                     _('cannot use collapse with continue or abort'))
             if srcf or basef or destf:
                 raise error.Abort(
                     _('abort and continue do not allow specifying revisions'))
             if abortf and opts.get('tool', False):
                 ui.warn(_('tool option will be ignored\n'))
             if contf:
                 ms = mergemod.mergestate.read(repo)
                 mergeutil.checkunresolved(ms)
 
             retcode = rbsrt._prepareabortorcontinue(abortf)
             if retcode is not None:
                 return retcode
         else:
             dest, rebaseset = _definesets(ui, repo, destf, srcf, basef, revf,
                                           destspace=destspace)
             retcode = rbsrt._preparenewrebase(dest, rebaseset)
             if retcode is not None:
                 return retcode
 
         rbsrt._performrebase()
         rbsrt._finishrebase()
     finally:
         release(lock, wlock)
 
 def _definesets(ui, repo, destf=None, srcf=None, basef=None, revf=[],
                 destspace=None):
     """use revisions argument to define destination and rebase set
     """
     # destspace is here to work around issues with `hg pull --rebase` see
     # issue5214 for details
     if srcf and basef:
         raise error.Abort(_('cannot specify both a source and a base'))
     if revf and basef:
         raise error.Abort(_('cannot specify both a revision and a base'))
     if revf and srcf:
         raise error.Abort(_('cannot specify both a revision and a source'))
 
     cmdutil.checkunfinished(repo)
     cmdutil.bailifchanged(repo)
 
     if destf:
         dest = scmutil.revsingle(repo, destf)
 
     if revf:
         rebaseset = scmutil.revrange(repo, revf)
         if not rebaseset:
             ui.status(_('empty "rev" revision set - nothing to rebase\n'))
             return None, None
     elif srcf:
         src = scmutil.revrange(repo, [srcf])
         if not src:
             ui.status(_('empty "source" revision set - nothing to rebase\n'))
             return None, None
         rebaseset = repo.revs('(%ld)::', src)
         assert rebaseset
     else:
         base = scmutil.revrange(repo, [basef or '.'])
         if not base:
             ui.status(_('empty "base" revision set - '
                         "can't compute rebase set\n"))
             return None, None
         if not destf:
             dest = repo[_destrebase(repo, base, destspace=destspace)]
             destf = str(dest)
 
-        commonanc = repo.revs('ancestor(%ld, %d)', base, dest).first()
-        if commonanc is not None:
-            rebaseset = repo.revs('(%d::(%ld) - %d)::',
-                                  commonanc, base, commonanc)
-        else:
-            rebaseset = []
+        roots = [] # selected children of branching points
+        bpbase = {} # {branchingpoint: [origbase]}
+        for b in base: # group bases by branching points
+            bp = repo.revs('ancestor(%d, %d)', b, dest).first()
+            bpbase[bp] = bpbase.get(bp, []) + [b]
+        if None in bpbase:
+            # emulate the old behavior, showing "nothing to rebase" (a better
+            # behavior may be abort with "cannot find branching point" error)
+            bpbase.clear()
+        for bp, bs in bpbase.iteritems(): # calculate roots
+            roots += list(repo.revs('children(%d) & ancestors(%ld)', bp, bs))
+
+        rebaseset = repo.revs('%ld::', roots)
 
         if not rebaseset:
             # transform to list because smartsets are not comparable to
             # lists. This should be improved to honor laziness of
             # smartset.
             if list(base) == [dest.rev()]:
                 if basef:
                     ui.status(_('nothing to rebase - %s is both "base"'
                                 ' and destination\n') % dest)
                 else:
                     ui.status(_('nothing to rebase - working directory '
                                 'parent is also destination\n'))
             elif not repo.revs('%ld - ::%d', base, dest):
                 if basef:
                     ui.status(_('nothing to rebase - "base" %s is '
                                 'already an ancestor of destination '
                                 '%s\n') %
                               ('+'.join(str(repo[r]) for r in base),
                                dest))
                 else:
                     ui.status(_('nothing to rebase - working '
                                 'directory parent is already an '
                                 'ancestor of destination %s\n') % dest)
             else: # can it happen?
                 ui.status(_('nothing to rebase from %s to %s\n') %
                           ('+'.join(str(repo[r]) for r in base), dest))
             return None, None
 
     if not destf:
         dest = repo[_destrebase(repo, rebaseset, destspace=destspace)]
         destf = str(dest)
 
     return dest, rebaseset
 
 def externalparent(repo, state, targetancestors):
     """Return the revision that should be used as the second parent
     when the revisions in state is collapsed on top of targetancestors.
     Abort if there is more than one parent.
     """
     parents = set()
     source = min(state)
     for rev in state:
         if rev == source:
             continue
         for p in repo[rev].parents():
             if (p.rev() not in state
                         and p.rev() not in targetancestors):
                 parents.add(p.rev())
     if not parents:
         return nullrev
     if len(parents) == 1:
         return parents.pop()
     raise error.Abort(_('unable to collapse on top of %s, there is more '
                        'than one external parent: %s') %
                      (max(targetancestors),
                       ', '.join(str(p) for p in sorted(parents))))
 
 def concludenode(repo, rev, p1, p2, commitmsg=None, editor=None, extrafn=None,
                  keepbranches=False, date=None):
     '''Commit the wd changes with parents p1 and p2. Reuse commit info from rev
     but also store useful information in extra.
     Return node of committed revision.'''
     dsguard = dirstateguard.dirstateguard(repo, 'rebase')
     try:
         repo.setparents(repo[p1].node(), repo[p2].node())
         ctx = repo[rev]
         if commitmsg is None:
             commitmsg = ctx.description()
         keepbranch = keepbranches and repo[p1].branch() != ctx.branch()
         extra = {'rebase_source': ctx.hex()}
         if extrafn:
             extrafn(ctx, extra)
 
         backup = repo.ui.backupconfig('phases', 'new-commit')
         try:
             targetphase = max(ctx.phase(), phases.draft)
             repo.ui.setconfig('phases', 'new-commit', targetphase, 'rebase')
             if keepbranch:
                 repo.ui.setconfig('ui', 'allowemptycommit', True)
             # Commit might fail if unresolved files exist
             if date is None:
                 date = ctx.date()
             newnode = repo.commit(text=commitmsg, user=ctx.user(),
                                   date=date, extra=extra, editor=editor)
         finally:
             repo.ui.restoreconfig(backup)
 
         repo.dirstate.setbranch(repo[newnode].branch())
         dsguard.close()
         return newnode
     finally:
         release(dsguard)
 
 def rebasenode(repo, rev, p1, base, state, collapse, target):
     'Rebase a single revision rev on top of p1 using base as merge ancestor'
     # Merge phase
     # Update to target and merge it with local
     if repo['.'].rev() != p1:
         repo.ui.debug(" update to %d:%s\n" % (p1, repo[p1]))
         mergemod.update(repo, p1, False, True)
     else:
         repo.ui.debug(" already in target\n")
     repo.dirstate.write(repo.currenttransaction())
     repo.ui.debug(" merge against %d:%s\n" % (rev, repo[rev]))
     if base is not None:
         repo.ui.debug("   detach base %d:%s\n" % (base, repo[base]))
     # When collapsing in-place, the parent is the common ancestor, we
     # have to allow merging with it.
     stats = mergemod.update(repo, rev, True, True, base, collapse,
                             labels=['dest', 'source'])
     if collapse:
         copies.duplicatecopies(repo, rev, target)
     else:
         # If we're not using --collapse, we need to
         # duplicate copies between the revision we're
         # rebasing and its first parent, but *not*
         # duplicate any copies that have already been
         # performed in the destination.
         p1rev = repo[rev].p1().rev()
         copies.duplicatecopies(repo, rev, p1rev, skiprev=target)
     return stats
 
 def nearestrebased(repo, rev, state):
     """return the nearest ancestors of rev in the rebase result"""
     rebased = [r for r in state if state[r] > nullmerge]
     candidates = repo.revs('max(%ld  and (::%d))', rebased, rev)
     if candidates:
         return state[candidates.first()]
     else:
         return None
 
 def _checkobsrebase(repo, ui,
                                   rebaseobsrevs,
                                   rebasesetrevs,
                                   rebaseobsskipped):
     """
     Abort if rebase will create divergence or rebase is noop because of markers
 
     `rebaseobsrevs`: set of obsolete revision in source
     `rebasesetrevs`: set of revisions to be rebased from source
     `rebaseobsskipped`: set of revisions from source skipped because they have
     successors in destination
     """
     # Obsolete node with successors not in dest leads to divergence
     divergenceok = ui.configbool('experimental',
                                  'allowdivergence')
     divergencebasecandidates = rebaseobsrevs - rebaseobsskipped
 
     if divergencebasecandidates and not divergenceok:
         divhashes = (str(repo[r])
                      for r in divergencebasecandidates)
         msg = _("this rebase will cause "
                 "divergences from: %s")
         h = _("to force the rebase please set "
               "experimental.allowdivergence=True")
         raise error.Abort(msg % (",".join(divhashes),), hint=h)
 
 def defineparents(repo, rev, target, state, targetancestors,
                   obsoletenotrebased):
     'Return the new parent relationship of the revision that will be rebased'
     parents = repo[rev].parents()
     p1 = p2 = nullrev
     rp1 = None
 
     p1n = parents[0].rev()
     if p1n in targetancestors:
         p1 = target
     elif p1n in state:
         if state[p1n] == nullmerge:
             p1 = target
         elif state[p1n] in revskipped:
             p1 = nearestrebased(repo, p1n, state)
             if p1 is None:
                 p1 = target
         else:
             p1 = state[p1n]
     else: # p1n external
         p1 = target
         p2 = p1n
 
     if len(parents) == 2 and parents[1].rev() not in targetancestors:
         p2n = parents[1].rev()
         # interesting second parent
         if p2n in state:
             if p1 == target: # p1n in targetancestors or external
                 p1 = state[p2n]
                 if p1 == revprecursor:
                     rp1 = obsoletenotrebased[p2n]
             elif state[p2n] in revskipped:
                 p2 = nearestrebased(repo, p2n, state)
                 if p2 is None:
                     # no ancestors rebased yet, detach
                     p2 = target
             else:
                 p2 = state[p2n]
         else: # p2n external
             if p2 != nullrev: # p1n external too => rev is a merged revision
                 raise error.Abort(_('cannot use revision %d as base, result '
                         'would have 3 parents') % rev)
             p2 = p2n
     repo.ui.debug(" future parents are %d and %d\n" %
                             (repo[rp1 or p1].rev(), repo[p2].rev()))
 
     if not any(p.rev() in state for p in parents):
         # Case (1) root changeset of a non-detaching rebase set.
         # Let the merge mechanism find the base itself.
         base = None
     elif not repo[rev].p2():
         # Case (2) detaching the node with a single parent, use this parent
         base = repo[rev].p1().rev()
     else:
         # Assuming there is a p1, this is the case where there also is a p2.
         # We are thus rebasing a merge and need to pick the right merge base.
         #
         # Imagine we have:
         # - M: current rebase revision in this step
         # - A: one parent of M
         # - B: other parent of M
         # - D: destination of this merge step (p1 var)
         #
         # Consider the case where D is a descendant of A or B and the other is
         # 'outside'. In this case, the right merge base is the D ancestor.
         #
         # An informal proof, assuming A is 'outside' and B is the D ancestor:
         #
         # If we pick B as the base, the merge involves:
         # - changes from B to M (actual changeset payload)
         # - changes from B to D (induced by rebase) as D is a rebased
         #   version of B)
         # Which exactly represent the rebase operation.
         #
         # If we pick A as the base, the merge involves:
         # - changes from A to M (actual changeset payload)
         # - changes from A to D (with include changes between unrelated A and B
         #   plus changes induced by rebase)
         # Which does not represent anything sensible and creates a lot of
         # conflicts. A is thus not the right choice - B is.
         #
         # Note: The base found in this 'proof' is only correct in the specified
         # case. This base does not make sense if is not D a descendant of A or B
         # or if the other is not parent 'outside' (especially not if the other
         # parent has been rebased). The current implementation does not
         # make it feasible to consider different cases separately. In these
         # other cases we currently just leave it to the user to correctly
         # resolve an impossible merge using a wrong ancestor.
         #
         # xx, p1 could be -4, and both parents could probably be -4...
         for p in repo[rev].parents():
             if state.get(p.rev()) == p1:
                 base = p.rev()
                 break
         else: # fallback when base not found
             base = None
 
             # Raise because this function is called wrong (see issue 4106)
             raise AssertionError('no base found to rebase on '
                                  '(defineparents called wrong)')
     return rp1 or p1, p2, base
 
 def isagitpatch(repo, patchname):
     'Return true if the given patch is in git format'
     mqpatch = os.path.join(repo.mq.path, patchname)
     for line in patch.linereader(file(mqpatch, 'rb')):
         if line.startswith('diff --git'):
             return True
     return False
 
 def updatemq(repo, state, skipped, **opts):
     'Update rebased mq patches - finalize and then import them'
     mqrebase = {}
     mq = repo.mq
     original_series = mq.fullseries[:]
     skippedpatches = set()
 
     for p in mq.applied:
         rev = repo[p.node].rev()
         if rev in state:
             repo.ui.debug('revision %d is an mq patch (%s), finalize it.\n' %
                                         (rev, p.name))
             mqrebase[rev] = (p.name, isagitpatch(repo, p.name))
         else:
             # Applied but not rebased, not sure this should happen
             skippedpatches.add(p.name)
 
     if mqrebase:
         mq.finish(repo, mqrebase.keys())
 
         # We must start import from the newest revision
         for rev in sorted(mqrebase, reverse=True):
             if rev not in skipped:
                 name, isgit = mqrebase[rev]
                 repo.ui.note(_('updating mq patch %s to %s:%s\n') %
                              (name, state[rev], repo[state[rev]]))
                 mq.qimport(repo, (), patchname=name, git=isgit,
                                 rev=[str(state[rev])])
             else:
                 # Rebased and skipped
                 skippedpatches.add(mqrebase[rev][0])
 
         # Patches were either applied and rebased and imported in
         # order, applied and removed or unapplied. Discard the removed
         # ones while preserving the original series order and guards.
         newseries = [s for s in original_series
                      if mq.guard_re.split(s, 1)[0] not in skippedpatches]
         mq.fullseries[:] = newseries
         mq.seriesdirty = True
         mq.savedirty()
 
 def updatebookmarks(repo, targetnode, nstate, originalbookmarks, tr):
     'Move bookmarks to their correct changesets, and delete divergent ones'
     marks = repo._bookmarks
     for k, v in originalbookmarks.iteritems():
         if v in nstate:
             # update the bookmarks for revs that have moved
             marks[k] = nstate[v]
             bookmarks.deletedivergent(repo, [targetnode], k)
     marks.recordchange(tr)
 
 def storecollapsemsg(repo, collapsemsg):
     'Store the collapse message to allow recovery'
     collapsemsg = collapsemsg or ''
     f = repo.vfs("last-message.txt", "w")
     f.write("%s\n" % collapsemsg)
     f.close()
 
 def clearcollapsemsg(repo):
     'Remove collapse message file'
     util.unlinkpath(repo.join("last-message.txt"), ignoremissing=True)
 
 def restorecollapsemsg(repo):
     'Restore previously stored collapse message'
     try:
         f = repo.vfs("last-message.txt")
         collapsemsg = f.readline().strip()
         f.close()
     except IOError as err:
         if err.errno != errno.ENOENT:
             raise
         raise error.Abort(_('no rebase in progress'))
     return collapsemsg
 
 def storestatus(repo, originalwd, target, state, collapse, keep, keepbranches,
                 external, activebookmark):
     'Store the current status to allow recovery'
     f = repo.vfs("rebasestate", "w")
     f.write(repo[originalwd].hex() + '\n')
     f.write(repo[target].hex() + '\n')
     f.write(repo[external].hex() + '\n')
     f.write('%d\n' % int(collapse))
     f.write('%d\n' % int(keep))
     f.write('%d\n' % int(keepbranches))
     f.write('%s\n' % (activebookmark or ''))
     for d, v in state.iteritems():
         oldrev = repo[d].hex()
         if v >= 0:
             newrev = repo[v].hex()
         elif v == revtodo:
             # To maintain format compatibility, we have to use nullid.
             # Please do remove this special case when upgrading the format.
             newrev = hex(nullid)
         else:
             newrev = v
         f.write("%s:%s\n" % (oldrev, newrev))
     f.close()
     repo.ui.debug('rebase status stored\n')
 
 def clearstatus(repo):
     'Remove the status files'
     _clearrebasesetvisibiliy(repo)
     util.unlinkpath(repo.join("rebasestate"), ignoremissing=True)
 
 def needupdate(repo, state):
     '''check whether we should `update --clean` away from a merge, or if
     somehow the working dir got forcibly updated, e.g. by older hg'''
     parents = [p.rev() for p in repo[None].parents()]
 
     # Are we in a merge state at all?
     if len(parents) < 2:
         return False
 
     # We should be standing on the first as-of-yet unrebased commit.
     firstunrebased = min([old for old, new in state.iteritems()
                           if new == nullrev])
     if firstunrebased in parents:
         return True
 
     return False
 
 def abort(repo, originalwd, target, state, activebookmark=None):
     '''Restore the repository to its original state.  Additional args:
 
     activebookmark: the name of the bookmark that should be active after the
         restore'''
 
     try:
         # If the first commits in the rebased set get skipped during the rebase,
         # their values within the state mapping will be the target rev id. The
         # dstates list must must not contain the target rev (issue4896)
         dstates = [s for s in state.values() if s >= 0 and s != target]
         immutable = [d for d in dstates if not repo[d].mutable()]
         cleanup = True
         if immutable:
             repo.ui.warn(_("warning: can't clean up public changesets %s\n")
                         % ', '.join(str(repo[r]) for r in immutable),
                         hint=_("see 'hg help phases' for details"))
             cleanup = False
 
         descendants = set()
         if dstates:
             descendants = set(repo.changelog.descendants(dstates))
         if descendants - set(dstates):
             repo.ui.warn(_("warning: new changesets detected on target branch, "
                         "can't strip\n"))
             cleanup = False
 
         if cleanup:
             shouldupdate = False
             rebased = filter(lambda x: x >= 0 and x != target, state.values())
             if rebased:
                 strippoints = [
                         c.node() for c in repo.set('roots(%ld)', rebased)]
                 shouldupdate = len([
                         c.node() for c in repo.set('. & (%ld)', rebased)]) > 0
 
             # Update away from the rebase if necessary
             if shouldupdate or needupdate(repo, state):
                 mergemod.update(repo, originalwd, False, True)
 
             # Strip from the first rebased revision
             if rebased:
                 # no backup of rebased cset versions needed
                 repair.strip(repo.ui, repo, strippoints)
 
         if activebookmark and activebookmark in repo._bookmarks:
             bookmarks.activate(repo, activebookmark)
 
     finally:
         clearstatus(repo)
         clearcollapsemsg(repo)
         repo.ui.warn(_('rebase aborted\n'))
     return 0
 
 def buildstate(repo, dest, rebaseset, collapse, obsoletenotrebased):
     '''Define which revisions are going to be rebased and where
 
     repo: repo
     dest: context
     rebaseset: set of rev
     '''
     _setrebasesetvisibility(repo, rebaseset)
 
     # This check isn't strictly necessary, since mq detects commits over an
     # applied patch. But it prevents messing up the working directory when
     # a partially completed rebase is blocked by mq.
     if 'qtip' in repo.tags() and (dest.node() in
                             [s.node for s in repo.mq.applied]):
         raise error.Abort(_('cannot rebase onto an applied mq patch'))
 
     roots = list(repo.set('roots(%ld)', rebaseset))
     if not roots:
         raise error.Abort(_('no matching revisions'))
     roots.sort()
     state = {}
     detachset = set()
     for root in roots:
         commonbase = root.ancestor(dest)
         if commonbase == root:
             raise error.Abort(_('source is ancestor of destination'))
         if commonbase == dest:
             samebranch = root.branch() == dest.branch()
             if not collapse and samebranch and root in dest.children():
                 repo.ui.debug('source is a child of destination\n')
                 return None
 
         repo.ui.debug('rebase onto %s starting from %s\n' % (dest, root))
         state.update(dict.fromkeys(rebaseset, revtodo))
         # Rebase tries to turn <dest> into a parent of <root> while
         # preserving the number of parents of rebased changesets:
         #
         # - A changeset with a single parent will always be rebased as a
         #   changeset with a single parent.
         #
         # - A merge will be rebased as merge unless its parents are both
         #   ancestors of <dest> or are themselves in the rebased set and
         #   pruned while rebased.
         #
         # If one parent of <root> is an ancestor of <dest>, the rebased
         # version of this parent will be <dest>. This is always true with
         # --base option.
         #
         # Otherwise, we need to *replace* the original parents with
         # <dest>. This "detaches" the rebased set from its former location
         # and rebases it onto <dest>. Changes introduced by ancestors of
         # <root> not common with <dest> (the detachset, marked as
         # nullmerge) are "removed" from the rebased changesets.
         #
         # - If <root> has a single parent, set it to <dest>.
         #
         # - If <root> is a merge, we cannot decide which parent to
         #   replace, the rebase operation is not clearly defined.
         #
         # The table below sums up this behavior:
         #
         # +------------------+----------------------+-------------------------+
         # |                  |     one parent       |  merge                  |
         # +------------------+----------------------+-------------------------+
         # | parent in        | new parent is <dest> | parents in ::<dest> are |
         # | ::<dest>         |                      | remapped to <dest>      |
         # +------------------+----------------------+-------------------------+
         # | unrelated source | new parent is <dest> | ambiguous, abort        |
         # +------------------+----------------------+-------------------------+
         #
         # The actual abort is handled by `defineparents`
         if len(root.parents()) <= 1:
             # ancestors of <root> not ancestors of <dest>
             detachset.update(repo.changelog.findmissingrevs([commonbase.rev()],
                                                             [root.rev()]))
     for r in detachset:
         if r not in state:
             state[r] = nullmerge
     if len(roots) > 1:
         # If we have multiple roots, we may have "hole" in the rebase set.
         # Rebase roots that descend from those "hole" should not be detached as
         # other root are. We use the special `revignored` to inform rebase that
         # the revision should be ignored but that `defineparents` should search
         # a rebase destination that make sense regarding rebased topology.
         rebasedomain = set(repo.revs('%ld::%ld', rebaseset, rebaseset))
         for ignored in set(rebasedomain) - set(rebaseset):
             state[ignored] = revignored
     for r in obsoletenotrebased:
         if obsoletenotrebased[r] is None:
             state[r] = revpruned
         else:
             state[r] = revprecursor
     return repo['.'].rev(), dest.rev(), state
 
 def clearrebased(ui, repo, state, skipped, collapsedas=None):
     """dispose of rebased revision at the end of the rebase
 
     If `collapsedas` is not None, the rebase was a collapse whose result if the
     `collapsedas` node."""
     if obsolete.isenabled(repo, obsolete.createmarkersopt):
         markers = []
         for rev, newrev in sorted(state.items()):
             if newrev >= 0:
                 if rev in skipped:
                     succs = ()
                 elif collapsedas is not None:
                     succs = (repo[collapsedas],)
                 else:
                     succs = (repo[newrev],)
                 markers.append((repo[rev], succs))
         if markers:
             obsolete.createmarkers(repo, markers)
     else:
         rebased = [rev for rev in state if state[rev] > nullmerge]
         if rebased:
             stripped = []
             for root in repo.set('roots(%ld)', rebased):
                 if set(repo.changelog.descendants([root.rev()])) - set(state):
                     ui.warn(_("warning: new changesets detected "
                               "on source branch, not stripping\n"))
                 else:
                     stripped.append(root.node())
             if stripped:
                 # backup the old csets by default
                 repair.strip(ui, repo, stripped, "all")
 
 
 def pullrebase(orig, ui, repo, *args, **opts):
     'Call rebase after pull if the latter has been invoked with --rebase'
     ret = None
     if opts.get('rebase'):
         wlock = lock = None
         try:
             wlock = repo.wlock()
             lock = repo.lock()
             if opts.get('update'):
                 del opts['update']
                 ui.debug('--update and --rebase are not compatible, ignoring '
                          'the update flag\n')
 
             revsprepull = len(repo)
             origpostincoming = commands.postincoming
             def _dummy(*args, **kwargs):
                 pass
             commands.postincoming = _dummy
             try:
                 ret = orig(ui, repo, *args, **opts)
             finally:
                 commands.postincoming = origpostincoming
             revspostpull = len(repo)
             if revspostpull > revsprepull:
                 # --rev option from pull conflict with rebase own --rev
                 # dropping it
                 if 'rev' in opts:
                     del opts['rev']
                 # positional argument from pull conflicts with rebase's own
                 # --source.
                 if 'source' in opts:
                     del opts['source']
                 # revsprepull is the len of the repo, not revnum of tip.
                 destspace = list(repo.changelog.revs(start=revsprepull))
                 opts['_destspace'] = destspace
                 try:
                     rebase(ui, repo, **opts)
                 except error.NoMergeDestAbort:
                     # we can maybe update instead
                     rev, _a, _b = destutil.destupdate(repo)
                     if rev == repo['.'].rev():
                         ui.status(_('nothing to rebase\n'))
                     else:
                         ui.status(_('nothing to rebase - updating instead\n'))
                         # not passing argument to get the bare update behavior
                         # with warning and trumpets
                         commands.update(ui, repo)
         finally:
             release(lock, wlock)
     else:
         if opts.get('tool'):
             raise error.Abort(_('--tool can only be used with --rebase'))
         ret = orig(ui, repo, *args, **opts)
 
     return ret
 
 def _setrebasesetvisibility(repo, revs):
     """store the currently rebased set on the repo object
 
     This is used by another function to prevent rebased revision to because
     hidden (see issue4505)"""
     repo = repo.unfiltered()
     revs = set(revs)
     repo._rebaseset = revs
     # invalidate cache if visibility changes
     hiddens = repo.filteredrevcache.get('visible', set())
     if revs & hiddens:
         repo.invalidatevolatilesets()
 
 def _clearrebasesetvisibiliy(repo):
     """remove rebaseset data from the repo"""
     repo = repo.unfiltered()
     if '_rebaseset' in vars(repo):
         del repo._rebaseset
 
 def _rebasedvisible(orig, repo):
     """ensure rebased revs stay visible (see issue4505)"""
     blockers = orig(repo)
     blockers.update(getattr(repo, '_rebaseset', ()))
     return blockers
 
 def _filterobsoleterevs(repo, revs):
     """returns a set of the obsolete revisions in revs"""
     return set(r for r in revs if repo[r].obsolete())
 
 def _computeobsoletenotrebased(repo, rebaseobsrevs, dest):
     """return a mapping obsolete => successor for all obsolete nodes to be
     rebased that have a successors in the destination
 
     obsolete => None entries in the mapping indicate nodes with no successor"""
     obsoletenotrebased = {}
 
     # Build a mapping successor => obsolete nodes for the obsolete
     # nodes to be rebased
     allsuccessors = {}
     cl = repo.changelog
     for r in rebaseobsrevs:
         node = cl.node(r)
         for s in obsolete.allsuccessors(repo.obsstore, [node]):
             try:
                 allsuccessors[cl.rev(s)] = cl.rev(node)
             except LookupError:
                 pass
 
     if allsuccessors:
         # Look for successors of obsolete nodes to be rebased among
         # the ancestors of dest
         ancs = cl.ancestors([repo[dest].rev()],
                             stoprev=min(allsuccessors),
                             inclusive=True)
         for s in allsuccessors:
             if s in ancs:
                 obsoletenotrebased[allsuccessors[s]] = s
             elif (s == allsuccessors[s] and
                   allsuccessors.values().count(s) == 1):
                 # plain prune
                 obsoletenotrebased[s] = None
 
     return obsoletenotrebased
 
 def summaryhook(ui, repo):
     if not os.path.exists(repo.join('rebasestate')):
         return
     try:
         rbsrt = rebaseruntime(repo, ui, {})
         rbsrt.restorestatus()
         state = rbsrt.state
     except error.RepoLookupError:
         # i18n: column positioning for "hg summary"
         msg = _('rebase: (use "hg rebase --abort" to clear broken state)\n')
         ui.write(msg)
         return
     numrebased = len([i for i in state.itervalues() if i >= 0])
     # i18n: column positioning for "hg summary"
     ui.write(_('rebase: %s, %s (rebase --continue)\n') %
              (ui.label(_('%d rebased'), 'rebase.rebased') % numrebased,
               ui.label(_('%d remaining'), 'rebase.remaining') %
               (len(state) - numrebased)))
 
 def uisetup(ui):
     #Replace pull with a decorator to provide --rebase option
     entry = extensions.wrapcommand(commands.table, 'pull', pullrebase)
     entry[1].append(('', 'rebase', None,
                      _("rebase working directory to branch head")))
     entry[1].append(('t', 'tool', '',
                      _("specify merge tool for rebase")))
     cmdutil.summaryhooks.add('rebase', summaryhook)
     cmdutil.unfinishedstates.append(
         ['rebasestate', False, False, _('rebase in progress'),
          _("use 'hg rebase --continue' or 'hg rebase --abort'")])
     cmdutil.afterresolvedstates.append(
         ['rebasestate', _('hg rebase --continue')])
     # ensure rebased rev are not hidden
     extensions.wrapfunction(repoview, '_getdynamicblockers', _rebasedvisible)