rebase: change internal format to support destination map

A later patch will add multiple destination support. This patch changes
internal state and the rebase state file format to support that. But the
external interface still only supports single destination.

A test was added to make sure rebase still supports legacy state file.

The new state file is incompatible with old clients. We had done similar
state file format change before: 5eac7ab, 92409f8, and 72412af. The state
file is transient, so the impact of incompatibility is limited. Besides,
the old client won't support multiple destinations anyway so it does not
really make sense to make the file format compatible with them.

Differential Revision: https://phab.mercurial-scm.org/D348

tests/test-rebase-legacy.t

@@ -0,0 +1,76 b''
+Test rebase --continue with rebasestate written by legacy client
+
+  $ cat >> $HGRCPATH <<EOF
+  > [extensions]
+  > rebase=
+  > drawdag=$TESTDIR/drawdag.py
+  > EOF
+
+  $ hg init
+  $ hg debugdrawdag <<'EOF'
+  >    D H
+  >    | |
+  >    C G
+  >    | |
+  >    B F
+  >    | |
+  >  Z A E
+  >   \|/
+  >    R
+  > EOF
+
+rebasestate generated by a legacy client running "hg rebase -r B+D+E+G+H -d Z"
+
+  $ touch .hg/last-message.txt
+  $ cat > .hg/rebasestate <<EOF
+  > 0000000000000000000000000000000000000000
+  > f424eb6a8c01c4a0c0fba9f863f79b3eb5b4b69f
+  > 0000000000000000000000000000000000000000
+  > 0
+  > 0
+  > 0
+  > 
+  > 21a6c45028857f500f56ae84fbf40689c429305b:-2
+  > de008c61a447fcfd93f808ef527d933a84048ce7:0000000000000000000000000000000000000000
+  > c1e6b162678d07d0b204e5c8267d51b4e03b633c:0000000000000000000000000000000000000000
+  > aeba276fcb7df8e10153a07ee728d5540693f5aa:-3
+  > bd5548558fcf354d37613005737a143871bf3723:-3
+  > d2fa1c02b2401b0e32867f26cce50818a4bd796a:0000000000000000000000000000000000000000
+  > 6f7a236de6852570cd54649ab62b1012bb78abc8:0000000000000000000000000000000000000000
+  > 6582e6951a9c48c236f746f186378e36f59f4928:0000000000000000000000000000000000000000
+  > EOF
+
+  $ hg rebase --continue
+  rebasing 4:c1e6b162678d "B" (B)
+  rebasing 8:6f7a236de685 "D" (D)
+  rebasing 2:de008c61a447 "E" (E)
+  rebasing 7:d2fa1c02b240 "G" (G)
+  rebasing 9:6582e6951a9c "H" (H tip)
+  warning: orphaned descendants detected, not stripping c1e6b162678d, de008c61a447
+  saved backup bundle to $TESTTMP/.hg/strip-backup/6f7a236de685-9880a3dc-rebase.hg (glob)
+
+  $ hg log -G -T '{rev}:{node|short} {desc}\n'
+  o  11:721b8da0a708 H
+  |
+  o  10:9d65695ec3c2 G
+  |
+  o  9:21c8397a5d68 E
+  |
+  | o  8:fc52970345e8 D
+  | |
+  | o  7:eac96551b107 B
+  |/
+  | o  6:bd5548558fcf C
+  | |
+  | | o  5:aeba276fcb7d F
+  | | |
+  | o |  4:c1e6b162678d B
+  | | |
+  o | |  3:f424eb6a8c01 Z
+  | | |
+  +---o  2:de008c61a447 E
+  | |
+  | o  1:21a6c4502885 A
+  |/
+  o  0:b41ce7760717 R
+  

hgext/rebase.py

@@ -1,1541 +1,1570 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,
     obsutil,
     patch,
     phases,
     registrar,
     repair,
     repoview,
     revset,
     scmutil,
     smartset,
     util,
 )
 
 release = lock.release
 templateopts = cmdutil.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
+revtodostr = '-1'
 
 # legacy revstates no longer needed in current code
 # -2: nullmerge, -3: revignored, -4: revprecursor, -5: revpruned
 legacystates = {'-2', '-3', '-4', '-5'}
 
 cmdtable = {}
 command = registrar.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, smartset.fullreposet(repo), x)
     return subset & smartset.baseset([_destrebase(repo, sourceset)])
 
 def _ctxdesc(ctx):
     """short description for a context"""
     desc = '%d:%s "%s"' % (ctx.rev(), ctx,
                            ctx.description().split('\n', 1)[0])
     repo = ctx.repo()
     names = repo.nodetags(ctx.node()) + repo.nodebookmarks(ctx.node())
     if names:
         desc += ' (%s)' % ' '.join(names)
     return desc
 
 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.dest = None
+        self.destmap = {}
         self.skipped = 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 storestatus(self, tr=None):
         """Store the current status to allow recovery"""
         if tr:
             tr.addfilegenerator('rebasestate', ('rebasestate',),
                                 self._writestatus, location='plain')
         else:
             with self.repo.vfs("rebasestate", "w") as f:
                 self._writestatus(f)
 
     def _writestatus(self, f):
         repo = self.repo.unfiltered()
         f.write(repo[self.originalwd].hex() + '\n')
-        f.write(repo[self.dest].hex() + '\n')
+        # was "dest". we now write dest per src root below.
+        f.write('\n')
         f.write(repo[self.external].hex() + '\n')
         f.write('%d\n' % int(self.collapsef))
         f.write('%d\n' % int(self.keepf))
         f.write('%d\n' % int(self.keepbranchesf))
         f.write('%s\n' % (self.activebookmark or ''))
+        destmap = self.destmap
         for d, v in self.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))
+            destnode = repo[destmap[d]].hex()
+            f.write("%s:%s:%s\n" % (oldrev, newrev, destnode))
         repo.ui.debug('rebase status stored\n')
 
     def restorestatus(self):
         """Restore a previously stored status"""
         repo = self.repo
         keepbranches = None
-        dest = None
+        legacydest = None
         collapse = False
         external = nullrev
         activebookmark = None
         state = {}
+        destmap = {}
 
         try:
             f = repo.vfs("rebasestate")
             for i, l in enumerate(f.read().splitlines()):
                 if i == 0:
                     originalwd = repo[l].rev()
                 elif i == 1:
-                    dest = repo[l].rev()
+                    # this line should be empty in newer version. but legacy
+                    # clients may still use it
+                    if l:
+                        legacydest = 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(':')
+                    args = l.split(':')
+                    oldrev = args[0]
+                    newrev = args[1]
                     if newrev in legacystates:
                         continue
-                    elif newrev == nullid:
+                    if len(args) > 2:
+                        destnode = args[2]
+                    else:
+                        destnode = legacydest
+                    destmap[repo[oldrev].rev()] = repo[destnode].rev()
+                    if newrev in (nullid, revtodostr):
                         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 = {dest}
+            seen = set(destmap.values())
             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, set(state.keys()) | {originalwd})
 
         self.originalwd = originalwd
-        self.dest = dest
+        self.destmap = destmap
         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, dest):
+    def _handleskippingobsolete(self, obsoleterevs, destmap):
         """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
-        dest:           a destination revision for the rebase operation
+        destmap:        {srcrev: destrev} destination revisions
         """
         self.obsoletenotrebased = {}
         if not self.ui.configbool('experimental', 'rebaseskipobsolete',
                                   default=True):
             return
         obsoleteset = set(obsoleterevs)
         self.obsoletenotrebased = _computeobsoletenotrebased(self.repo,
-                                    obsoleteset, dest)
+                                    obsoleteset, destmap)
         skippedset = set(self.obsoletenotrebased)
         _checkobsrebase(self.repo, self.ui, obsoleteset, skippedset)
 
     def _prepareabortorcontinue(self, isabort):
         try:
             self.restorestatus()
             self.collapsemsg = restorecollapsemsg(self.repo, isabort)
         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.dest,
+            return abort(self.repo, self.originalwd, self.destmap,
                          self.state, activebookmark=self.activebookmark)
 
-    def _preparenewrebase(self, dest, rebaseset):
-        if dest is None:
+    def _preparenewrebase(self, destmap):
+        if not destmap:
             return _nothingtorebase()
 
+        rebaseset = destmap.keys()
         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.rev())
+        obsrevs = _filterobsoleterevs(self.repo, rebaseset)
+        self._handleskippingobsolete(obsrevs, destmap)
 
-        result = buildstate(self.repo, dest, rebaseset, self.collapsef,
+        result = buildstate(self.repo, destmap, self.collapsef,
                             self.obsoletenotrebased)
 
         if not result:
             # Empty state built, nothing to rebase
             self.ui.status(_('nothing to rebase\n'))
             return _nothingtorebase()
 
         for root in self.repo.set('roots(%ld)', rebaseset):
             if not self.keepf and not root.mutable():
                 raise error.Abort(_("can't rebase public changeset %s")
                                   % root,
                                   hint=_("see 'hg help phases' for details"))
 
-        (self.originalwd, self.dest, self.state) = result
+        (self.originalwd, self.destmap, self.state) = result
         if self.collapsef:
-            destancestors = self.repo.changelog.ancestors([self.dest],
+            dests = set(self.destmap.values())
+            if len(dests) != 1:
+                raise error.Abort(
+                    _('--collapse does not work with multiple destinations'))
+            destrev = next(iter(dests))
+            destancestors = self.repo.changelog.ancestors([destrev],
                                                           inclusive=True)
             self.external = externalparent(self.repo, self.state, destancestors)
 
+        for destrev in sorted(set(destmap.values())):
+            dest = self.repo[destrev]
         if dest.closesbranch() and not self.keepbranchesf:
             self.ui.status(_('reopening closed branch head %s\n') % dest)
 
     def _performrebase(self, tr):
         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'))
 
         # Keep track of the active bookmarks in order to reset them later
         self.activebookmark = self.activebookmark or repo._activebookmark
         if self.activebookmark:
             bookmarks.deactivate(repo)
 
         # Store the state before we begin so users can run 'hg rebase --abort'
         # if we fail before the transaction closes.
         self.storestatus()
 
         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:
+            dest = self.destmap[rev]
             ctx = repo[rev]
             desc = _ctxdesc(ctx)
             if self.state[rev] == rev:
                 ui.status(_('already rebased %s\n') % desc)
             elif 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.dest, self.state)
+                p1, p2, base = defineparents(repo, rev, self.destmap,
+                                             self.state)
                 self.storestatus(tr=tr)
                 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.dest)
+                                           self.collapsef, dest)
                         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)
                     if newnode is None:
                         # If it ended up being a no-op commit, then the normal
                         # merge state clean-up path doesn't happen, so do it
                         # here. Fix issue5494
                         mergemod.mergestate.clean(repo)
                 else:
                     # Skip commit if we are collapsing
                     repo.setparents(repo[p1].node())
                     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)
             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.dest, self.state)
+            p1, p2, _base = defineparents(repo, min(self.state), self.destmap,
+                                          self.state)
             editopt = opts.get('edit')
             editform = 'rebase.collapse'
             if self.collapsemsg:
                 commitmsg = self.collapsemsg
             else:
                 commitmsg = 'Collapsed revision'
                 for rebased in sorted(self.state):
                     if rebased not in self.skipped:
                         commitmsg += '\n* %s' % repo[rebased].description()
                 editopt = True
             editor = cmdutil.getcommiteditor(edit=editopt, editform=editform)
             revtoreuse = max(self.state)
 
             dsguard = None
             if ui.configbool('rebase', 'singletransaction'):
                 dsguard = dirstateguard.dirstateguard(repo, 'rebase')
             with util.acceptintervention(dsguard):
                 newnode = concludenode(repo, revtoreuse, p1, self.external,
                                        commitmsg=commitmsg,
                                        extrafn=_makeextrafn(self.extrafns),
                                        editor=editor,
                                        keepbranches=self.keepbranchesf,
                                        date=self.date)
             if newnode is not None:
                 newrev = repo[newnode].rev()
                 for oldrev in self.state.iterkeys():
                     self.state[oldrev] = newrev
 
         if 'qtip' in repo.tags():
             updatemq(repo, self.state, self.skipped, **opts)
 
         # restore original working directory
         # (we do this before stripping)
         newwd = self.state.get(self.originalwd, self.originalwd)
         if 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 not self.keepf:
             collapsedas = None
             if self.collapsef:
                 collapsedas = newnode
-            clearrebased(ui, repo, self.dest, self.state, self.skipped,
+            clearrebased(ui, repo, self.destmap, 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 self.activebookmark in repo._bookmarks 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
 
     Configuration Options:
 
     You can make rebase require a destination if you set the following config
     option::
 
       [commands]
       rebase.requiredest = True
 
     By default, rebase will close the transaction after each commit. For
     performance purposes, you can configure rebase to use a single transaction
     across the entire rebase. WARNING: This setting introduces a significant
     risk of losing the work you've done in a rebase if the rebase aborts
     unexpectedly::
 
       [rebase]
       singletransaction = True
 
     Return Values:
 
     Returns 0 on success, 1 if nothing to rebase or there are
     unresolved conflicts.
 
     """
     rbsrt = rebaseruntime(repo, ui, opts)
 
     with repo.wlock(), 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,
+            destmap = _definedestmap(ui, repo, destf, srcf, basef, revf,
                                           destspace=destspace)
-            retcode = rbsrt._preparenewrebase(dest, rebaseset)
+            retcode = rbsrt._preparenewrebase(destmap)
             if retcode is not None:
                 return retcode
 
         tr = None
         dsguard = None
 
         singletr = ui.configbool('rebase', 'singletransaction')
         if singletr:
             tr = repo.transaction('rebase')
         with util.acceptintervention(tr):
             if singletr:
                 dsguard = dirstateguard.dirstateguard(repo, 'rebase')
             with util.acceptintervention(dsguard):
                 rbsrt._performrebase(tr)
 
         rbsrt._finishrebase()
 
-def _definesets(ui, repo, destf=None, srcf=None, basef=None, revf=None,
+def _definedestmap(ui, repo, destf=None, srcf=None, basef=None, revf=None,
                 destspace=None):
-    """use revisions argument to define destination and rebase set
-    """
+    """use revisions argument to define destmap {srcrev: destrev}"""
     if revf is None:
         revf = []
 
     # 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 ui.configbool('commands', 'rebase.requiredest') and not destf:
         raise error.Abort(_('you must specify a destination'),
                           hint=_('use: hg rebase -d REV'))
 
     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
+            return None
     elif srcf:
         src = scmutil.revrange(repo, [srcf])
         if not src:
             ui.status(_('empty "source" revision set - nothing to rebase\n'))
-            return None, None
+            return 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
+            return None
         if not destf:
             dest = repo[_destrebase(repo, base, destspace=destspace)]
             destf = str(dest)
 
         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
+            return None
 
     if not destf:
         dest = repo[_destrebase(repo, rebaseset, destspace=destspace)]
         destf = str(dest)
 
-    return dest, rebaseset
+    # assign dest to each rev in rebaseset
+    destrev = dest.rev()
+    destmap = {r: destrev for r in rebaseset} # {srcrev: destrev}
+
+    return destmap
 
 def externalparent(repo, state, destancestors):
     """Return the revision that should be used as the second parent
     when the revisions in state is collapsed on top of destancestors.
     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 destancestors):
                 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(destancestors),
                       ', '.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 = util.nullcontextmanager()
     if not repo.ui.configbool('rebase', 'singletransaction'):
         dsguard = dirstateguard.dirstateguard(repo, 'rebase')
     with dsguard:
         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)
 
         destphase = max(ctx.phase(), phases.draft)
         overrides = {('phases', 'new-commit'): destphase}
         with repo.ui.configoverride(overrides, '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)
 
         repo.dirstate.setbranch(repo[newnode].branch())
         return newnode
 
 def rebasenode(repo, rev, p1, base, state, collapse, dest):
     'Rebase a single revision rev on top of p1 using base as merge ancestor'
     # Merge phase
     # Update to destination 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 destination\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, dest)
     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=dest)
     return stats
 
-def adjustdest(repo, rev, dest, state):
+def adjustdest(repo, rev, destmap, state):
     """adjust rebase destination given the current rebase state
 
     rev is what is being rebased. Return a list of two revs, which are the
     adjusted destinations for rev's p1 and p2, respectively. If a parent is
     nullrev, return dest without adjustment for it.
 
     For example, when doing rebase -r B+E -d F, rebase will first move B to B1,
     and E's destination will be adjusted from F to B1.
 
         B1 <- written during rebasing B
         |
         F <- original destination of B, E
         |
         | E <- rev, which is being rebased
         | |
         | D <- prev, one parent of rev being checked
         | |
         | x <- skipped, ex. no successor or successor in (::dest)
         | |
         | C
         | |
         | B <- rebased as B1
         |/
         A
 
     Another example about merge changeset, rebase -r C+G+H -d K, rebase will
     first move C to C1, G to G1, and when it's checking H, the adjusted
     destinations will be [C1, G1].
 
             H       C1 G1
            /|       | /
           F G       |/
         K | |  ->   K
         | C D       |
         | |/        |
         | B         | ...
         |/          |/
         A           A
     """
-    # pick already rebased revs from state
-    source = [s for s, d in state.items() if d > 0]
+    # pick already rebased revs with same dest from state as interesting source
+    dest = destmap[rev]
+    source = [s for s, d in state.items() if d > 0 and destmap[s] == dest]
 
     result = []
     for prev in repo.changelog.parentrevs(rev):
         adjusted = dest
         if prev != nullrev:
             candidate = repo.revs('max(%ld and (::%d))', source, prev).first()
             if candidate is not None:
                 adjusted = state[candidate]
         result.append(adjusted)
     return result
 
 def _checkobsrebase(repo, ui, rebaseobsrevs, rebaseobsskipped):
     """
     Abort if rebase will create divergence or rebase is noop because of markers
 
     `rebaseobsrevs`: set of obsolete revision in 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 successorrevs(repo, rev):
     """yield revision numbers for successors of rev"""
     unfi = repo.unfiltered()
     nodemap = unfi.changelog.nodemap
     for s in obsutil.allsuccessors(unfi.obsstore, [unfi[rev].node()]):
         if s in nodemap:
             yield nodemap[s]
 
-def defineparents(repo, rev, dest, state):
+def defineparents(repo, rev, destmap, state):
     """Return new parents and optionally a merge base for rev being rebased
 
     The destination specified by "dest" cannot always be used directly because
     previously rebase result could affect destination. For example,
 
           D E    rebase -r C+D+E -d B
           |/     C will be rebased to C'
         B C      D's new destination will be C' instead of B
         |/       E's new destination will be C' instead of B
         A
 
     The new parents of a merge is slightly more complicated. See the comment
     block below.
     """
     cl = repo.changelog
     def isancestor(a, b):
         # take revision numbers instead of nodes
         if a == b:
             return True
         elif a > b:
             return False
         return cl.isancestor(cl.node(a), cl.node(b))
 
+    dest = destmap[rev]
     oldps = repo.changelog.parentrevs(rev) # old parents
     newps = [nullrev, nullrev] # new parents
-    dests = adjustdest(repo, rev, dest, state) # adjusted destinations
+    dests = adjustdest(repo, rev, destmap, state) # adjusted destinations
     bases = list(oldps) # merge base candidates, initially just old parents
 
     if all(r == nullrev for r in oldps[1:]):
         # For non-merge changeset, just move p to adjusted dest as requested.
         newps[0] = dests[0]
     else:
         # For merge changeset, if we move p to dests[i] unconditionally, both
         # parents may change and the end result looks like "the merge loses a
         # parent", which is a surprise. This is a limit because "--dest" only
         # accepts one dest per src.
         #
         # Therefore, only move p with reasonable conditions (in this order):
         #   1. use dest, if dest is a descendent of (p or one of p's successors)
         #   2. use p's rebased result, if p is rebased (state[p] > 0)
         #
         # Comparing with adjustdest, the logic here does some additional work:
         #   1. decide which parents will not be moved towards dest
         #   2. if the above decision is "no", should a parent still be moved
         #      because it was rebased?
         #
         # For example:
         #
         #     C    # "rebase -r C -d D" is an error since none of the parents
         #    /|    # can be moved. "rebase -r B+C -d D" will move C's parent
         #   A B D  # B (using rule "2."), since B will be rebased.
         #
         # The loop tries to be not rely on the fact that a Mercurial node has
         # at most 2 parents.
         for i, p in enumerate(oldps):
             np = p # new parent
             if any(isancestor(x, dests[i]) for x in successorrevs(repo, p)):
                 np = dests[i]
             elif p in state and state[p] > 0:
                 np = state[p]
 
             # "bases" only record "special" merge bases that cannot be
             # calculated from changelog DAG (i.e. isancestor(p, np) is False).
             # For example:
             #
             #   B'   # rebase -s B -d D, when B was rebased to B'. dest for C
             #   | C  # is B', but merge base for C is B, instead of
             #   D |  # changelog.ancestor(C, B') == A. If changelog DAG and
             #   | B  # "state" edges are merged (so there will be an edge from
             #   |/   # B to B'), the merge base is still ancestor(C, B') in
             #   A    # the merged graph.
             #
             # Also see https://bz.mercurial-scm.org/show_bug.cgi?id=1950#c8
             # which uses "virtual null merge" to explain this situation.
             if isancestor(p, np):
                 bases[i] = nullrev
 
             # If one parent becomes an ancestor of the other, drop the ancestor
             for j, x in enumerate(newps[:i]):
                 if x == nullrev:
                     continue
                 if isancestor(np, x): # CASE-1
                     np = nullrev
                 elif isancestor(x, np): # CASE-2
                     newps[j] = np
                     np = nullrev
                     # New parents forming an ancestor relationship does not
                     # mean the old parents have a similar relationship. Do not
                     # set bases[x] to nullrev.
                     bases[j], bases[i] = bases[i], bases[j]
 
             newps[i] = np
 
         # "rebasenode" updates to new p1, and the old p1 will be used as merge
         # base. If only p2 changes, merging using unchanged p1 as merge base is
         # suboptimal. Therefore swap parents to make the merge sane.
         if newps[1] != nullrev and oldps[0] == newps[0]:
             assert len(newps) == 2 and len(oldps) == 2
             newps.reverse()
             bases.reverse()
 
         # No parent change might be an error because we fail to make rev a
         # descendent of requested dest. This can happen, for example:
         #
         #     C    # rebase -r C -d D
         #    /|    # None of A and B will be changed to D and rebase fails.
         #   A B D
         if set(newps) == set(oldps) and dest not in newps:
             raise error.Abort(_('cannot rebase %d:%s without '
                                 'moving at least one of its parents')
                               % (rev, repo[rev]))
 
     # "rebasenode" updates to new p1, use the corresponding merge base.
     if bases[0] != nullrev:
         base = bases[0]
     else:
         base = None
 
     # Check if the merge will contain unwanted changes. That may happen if
     # there are multiple special (non-changelog ancestor) merge bases, which
     # cannot be handled well by the 3-way merge algorithm. For example:
     #
     #     F
     #    /|
     #   D E  # "rebase -r D+E+F -d Z", when rebasing F, if "D" was chosen
     #   | |  # as merge base, the difference between D and F will include
     #   B C  # C, so the rebased F will contain C surprisingly. If "E" was
     #   |/   #  chosen, the rebased F will contain B.
     #   A Z
     #
     # But our merge base candidates (D and E in above case) could still be
     # better than the default (ancestor(F, Z) == null). Therefore still
     # pick one (so choose p1 above).
     if sum(1 for b in bases if b != nullrev) > 1:
         unwanted = [None, None] # unwanted[i]: unwanted revs if choose bases[i]
         for i, base in enumerate(bases):
             if base == nullrev:
                 continue
             # Revisions in the side (not chosen as merge base) branch that
             # might contain "surprising" contents
             siderevs = list(repo.revs('((%ld-%d) %% (%d+%d))',
                                       bases, base, base, dest))
 
             # If those revisions are covered by rebaseset, the result is good.
             # A merge in rebaseset would be considered to cover its ancestors.
             if siderevs:
                 rebaseset = [r for r, d in state.items() if d > 0]
                 merges = [r for r in rebaseset
                           if cl.parentrevs(r)[1] != nullrev]
                 unwanted[i] = list(repo.revs('%ld - (::%ld) - %ld',
                                              siderevs, merges, rebaseset))
 
         # Choose a merge base that has a minimal number of unwanted revs.
         l, i = min((len(revs), i)
                    for i, revs in enumerate(unwanted) if revs is not None)
         base = bases[i]
 
         # newps[0] should match merge base if possible. Currently, if newps[i]
         # is nullrev, the only case is newps[i] and newps[j] (j < i), one is
         # the other's ancestor. In that case, it's fine to not swap newps here.
         # (see CASE-1 and CASE-2 above)
         if i != 0 and newps[i] != nullrev:
             newps[0], newps[i] = newps[i], newps[0]
 
         # The merge will include unwanted revisions. Abort now. Revisit this if
         # we have a more advanced merge algorithm that handles multiple bases.
         if l > 0:
             unwanteddesc = _(' or ').join(
                 (', '.join('%d:%s' % (r, repo[r]) for r in revs)
                  for revs in unwanted if revs is not None))
             raise error.Abort(
                 _('rebasing %d:%s will include unwanted changes from %s')
                 % (rev, repo[rev], unwanteddesc))
 
     repo.ui.debug(" future parents are %d and %d\n" % tuple(newps))
 
     return newps[0], newps[1], 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 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'
     repo.vfs.unlinkpath("last-message.txt", ignoremissing=True)
 
 def restorecollapsemsg(repo, isabort):
     '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
         if isabort:
             # Oh well, just abort like normal
             collapsemsg = ''
         else:
             raise error.Abort(_('missing .hg/last-message.txt for rebase'))
     return collapsemsg
 
 def clearstatus(repo):
     'Remove the status files'
     _clearrebasesetvisibiliy(repo)
     # Make sure the active transaction won't write the state file
     tr = repo.currenttransaction()
     if tr:
         tr.removefilegenerator('rebasestate')
     repo.vfs.unlinkpath("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, dest, state, activebookmark=None):
+def abort(repo, originalwd, destmap, 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 dest rev id. The
         # dstates list must must not contain the dest rev (issue4896)
-        dstates = [s for s in state.values() if s >= 0 and s != dest]
+        dstates = [s for r, s in state.items() if s >= 0 and s != destmap[r]]
         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 destination "
                            "branch, can't strip\n"))
             cleanup = False
 
         if cleanup:
             shouldupdate = False
-            rebased = filter(lambda x: x >= 0 and x != dest, state.values())
+            rebased = [s for r, s in state.items()
+                       if s >= 0 and s != destmap[r]]
             if rebased:
                 strippoints = [
                         c.node() for c in repo.set('roots(%ld)', rebased)]
 
             updateifonnodes = set(rebased)
-            updateifonnodes.add(dest)
+            updateifonnodes.update(destmap.values())
             updateifonnodes.add(originalwd)
             shouldupdate = repo['.'].rev() in updateifonnodes
 
             # 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):
+def buildstate(repo, destmap, collapse, obsoletenotrebased):
     '''Define which revisions are going to be rebased and where
 
     repo: repo
-    dest: context
-    rebaseset: set of rev
+    destmap: {srcrev: destrev}
     '''
+    rebaseset = destmap.keys()
     originalwd = repo['.'].rev()
     _setrebasesetvisibility(repo, set(rebaseset) | {originalwd})
 
     # 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]):
+    if 'qtip' in repo.tags():
+        mqapplied = set(repo[s.node].rev() for s in repo.mq.applied)
+        if set(destmap.values()) & mqapplied:
         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 = dict.fromkeys(rebaseset, revtodo)
     emptyrebase = True
     for root in roots:
+        dest = repo[destmap[root.rev()]]
         commonbase = root.ancestor(dest)
         if commonbase == root:
             raise error.Abort(_('source is ancestor of destination'))
         if commonbase == dest:
             wctx = repo[None]
             if dest == wctx.p1():
                 # when rebasing to '.', it will use the current wd branch name
                 samebranch = root.branch() == wctx.branch()
             else:
                 samebranch = root.branch() == dest.branch()
             if not collapse and samebranch and dest in root.parents():
                 # mark the revision as done by setting its new revision
                 # equal to its old (current) revisions
                 state[root.rev()] = root.rev()
                 repo.ui.debug('source is a child of destination\n')
                 continue
 
         emptyrebase = False
         repo.ui.debug('rebase onto %s starting from %s\n' % (dest, root))
     if emptyrebase:
         return None
     for rev in sorted(state):
         parents = [p for p in repo.changelog.parentrevs(rev) if p != nullrev]
         # if all parents of this revision are done, then so is this revision
         if parents and all((state.get(p) == p for p in parents)):
             state[rev] = rev
     unfi = repo.unfiltered()
     for r in obsoletenotrebased:
         desc = _ctxdesc(unfi[r])
         succ = obsoletenotrebased[r]
         if succ is None:
             msg = _('note: not rebasing %s, it has no successor\n') % desc
             del state[r]
+            del destmap[r]
         else:
             destctx = unfi[succ]
             destdesc = '%d:%s "%s"' % (destctx.rev(), destctx,
                                        destctx.description().split('\n', 1)[0])
             msg = (_('note: not rebasing %s, already in destination as %s\n')
                    % (desc, destdesc))
             del state[r]
+            del destmap[r]
         repo.ui.status(msg)
-    return originalwd, dest.rev(), state
+    return originalwd, destmap, state
 
-def clearrebased(ui, repo, dest, state, skipped, collapsedas=None):
+def clearrebased(ui, repo, destmap, 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."""
     tonode = repo.changelog.node
     # Move bookmark of skipped nodes to destination. This cannot be handled
     # by scmutil.cleanupnodes since it will treat rev as removed (no successor)
     # and move bookmark backwards.
-    bmchanges = [(name, tonode(max(adjustdest(repo, rev, dest, state))))
+    bmchanges = [(name, tonode(max(adjustdest(repo, rev, destmap, state))))
                  for rev in skipped
                  for name in repo.nodebookmarks(tonode(rev))]
     if bmchanges:
         with repo.transaction('rebase') as tr:
             repo._bookmarks.applychanges(repo, tr, bmchanges)
     mapping = {}
     for rev, newrev in sorted(state.items()):
         if newrev >= 0 and newrev != rev:
             if rev in skipped:
                 succs = ()
             elif collapsedas is not None:
                 succs = (collapsedas,)
             else:
                 succs = (tonode(newrev),)
             mapping[tonode(rev)] = succs
     scmutil.cleanupnodes(repo, mapping, 'rebase')
 
 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'):
         if ui.configbool('commands', 'rebase.requiredest'):
             msg = _('rebase destination required by configuration')
             hint = _('use hg pull followed by hg rebase -d DEST')
             raise error.Abort(msg, hint=hint)
 
         with repo.wlock(), repo.lock():
             if opts.get('update'):
                 del opts['update']
                 ui.debug('--update and --rebase are not compatible, ignoring '
                          'the update flag\n')
 
             cmdutil.checkunfinished(repo)
             cmdutil.bailifchanged(repo, hint=_('cannot pull with rebase: '
                 'please commit or shelve your changes first'))
 
             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)
     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 issue4504)"""
     repo = repo.unfiltered()
     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 issue4504)"""
     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):
+def _computeobsoletenotrebased(repo, rebaseobsrevs, destmap):
     """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 = {}
 
     cl = repo.unfiltered().changelog
     nodemap = cl.nodemap
-    destnode = cl.node(dest)
     for srcrev in rebaseobsrevs:
         srcnode = cl.node(srcrev)
+        destnode = cl.node(destmap[srcrev])
         # XXX: more advanced APIs are required to handle split correctly
         successors = list(obsutil.allsuccessors(repo.obsstore, [srcnode]))
         if len(successors) == 1:
             # obsutil.allsuccessors includes node itself. When the list only
             # contains one element, it means there are no successors.
             obsoletenotrebased[srcrev] = None
         else:
             for succnode in successors:
                 if succnode == srcnode or succnode not in nodemap:
                     continue
                 if cl.isancestor(succnode, destnode):
                     obsoletenotrebased[srcrev] = nodemap[succnode]
                     break
 
     return obsoletenotrebased
 
 def summaryhook(ui, repo):
     if not repo.vfs.exists('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, 'pinnedrevs', _rebasedvisible)