bundle2: allow extensions to plug into the push process

Extensions are offered functions to add parts and process their results.

mercurial/exchange.py

@@ -1,721 +1,737
 # exchange.py - utility to exchange data between repos.
 #
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from i18n import _
 from node import hex, nullid
 import errno, urllib
 import util, scmutil, changegroup, base85
 import discovery, phases, obsolete, bookmarks, bundle2
 
 def readbundle(ui, fh, fname, vfs=None):
     header = changegroup.readexactly(fh, 4)
 
     alg = None
     if not fname:
         fname = "stream"
         if not header.startswith('HG') and header.startswith('\0'):
             fh = changegroup.headerlessfixup(fh, header)
             header = "HG10"
             alg = 'UN'
     elif vfs:
         fname = vfs.join(fname)
 
     magic, version = header[0:2], header[2:4]
 
     if magic != 'HG':
         raise util.Abort(_('%s: not a Mercurial bundle') % fname)
     if version == '10':
         if alg is None:
             alg = changegroup.readexactly(fh, 2)
         return changegroup.unbundle10(fh, alg)
     elif version == '2X':
         return bundle2.unbundle20(ui, fh, header=magic + version)
     else:
         raise util.Abort(_('%s: unknown bundle version %s') % (fname, version))
 
 
 class pushoperation(object):
     """A object that represent a single push operation
 
     It purpose is to carry push related state and very common operation.
 
     A new should be created at the beginning of each push and discarded
     afterward.
     """
 
     def __init__(self, repo, remote, force=False, revs=None, newbranch=False):
         # repo we push from
         self.repo = repo
         self.ui = repo.ui
         # repo we push to
         self.remote = remote
         # force option provided
         self.force = force
         # revs to be pushed (None is "all")
         self.revs = revs
         # allow push of new branch
         self.newbranch = newbranch
         # did a local lock get acquired?
         self.locallocked = None
         # Integer version of the push result
         # - None means nothing to push
         # - 0 means HTTP error
         # - 1 means we pushed and remote head count is unchanged *or*
         #   we have outgoing changesets but refused to push
         # - other values as described by addchangegroup()
         self.ret = None
         # discover.outgoing object (contains common and outgoing data)
         self.outgoing = None
         # all remote heads before the push
         self.remoteheads = None
         # testable as a boolean indicating if any nodes are missing locally.
         self.incoming = None
         # set of all heads common after changeset bundle push
         self.commonheads = None
 
 def push(repo, remote, force=False, revs=None, newbranch=False):
     '''Push outgoing changesets (limited by revs) from a local
     repository to remote. Return an integer:
       - None means nothing to push
       - 0 means HTTP error
       - 1 means we pushed and remote head count is unchanged *or*
         we have outgoing changesets but refused to push
       - other values as described by addchangegroup()
     '''
     pushop = pushoperation(repo, remote, force, revs, newbranch)
     if pushop.remote.local():
         missing = (set(pushop.repo.requirements)
                    - pushop.remote.local().supported)
         if missing:
             msg = _("required features are not"
                     " supported in the destination:"
                     " %s") % (', '.join(sorted(missing)))
             raise util.Abort(msg)
 
     # there are two ways to push to remote repo:
     #
     # addchangegroup assumes local user can lock remote
     # repo (local filesystem, old ssh servers).
     #
     # unbundle assumes local user cannot lock remote repo (new ssh
     # servers, http servers).
 
     if not pushop.remote.canpush():
         raise util.Abort(_("destination does not support push"))
     # get local lock as we might write phase data
     locallock = None
     try:
         locallock = pushop.repo.lock()
         pushop.locallocked = True
     except IOError, err:
         pushop.locallocked = False
         if err.errno != errno.EACCES:
             raise
         # source repo cannot be locked.
         # We do not abort the push, but just disable the local phase
         # synchronisation.
         msg = 'cannot lock source repository: %s\n' % err
         pushop.ui.debug(msg)
     try:
         pushop.repo.checkpush(pushop)
         lock = None
         unbundle = pushop.remote.capable('unbundle')
         if not unbundle:
             lock = pushop.remote.lock()
         try:
             _pushdiscovery(pushop)
             if _pushcheckoutgoing(pushop):
                 pushop.repo.prepushoutgoinghooks(pushop.repo,
                                                  pushop.remote,
                                                  pushop.outgoing)
                 if (pushop.repo.ui.configbool('experimental', 'bundle2-exp',
                                               False)
                     and pushop.remote.capable('bundle2-exp')):
                     _pushbundle2(pushop)
                 else:
                     _pushchangeset(pushop)
             _pushcomputecommonheads(pushop)
             _pushsyncphase(pushop)
             _pushobsolete(pushop)
         finally:
             if lock is not None:
                 lock.release()
     finally:
         if locallock is not None:
             locallock.release()
 
     _pushbookmark(pushop)
     return pushop.ret
 
 def _pushdiscovery(pushop):
     # discovery
     unfi = pushop.repo.unfiltered()
     fci = discovery.findcommonincoming
     commoninc = fci(unfi, pushop.remote, force=pushop.force)
     common, inc, remoteheads = commoninc
     fco = discovery.findcommonoutgoing
     outgoing = fco(unfi, pushop.remote, onlyheads=pushop.revs,
                    commoninc=commoninc, force=pushop.force)
     pushop.outgoing = outgoing
     pushop.remoteheads = remoteheads
     pushop.incoming = inc
 
 def _pushcheckoutgoing(pushop):
     outgoing = pushop.outgoing
     unfi = pushop.repo.unfiltered()
     if not outgoing.missing:
         # nothing to push
         scmutil.nochangesfound(unfi.ui, unfi, outgoing.excluded)
         return False
     # something to push
     if not pushop.force:
         # if repo.obsstore == False --> no obsolete
         # then, save the iteration
         if unfi.obsstore:
             # this message are here for 80 char limit reason
             mso = _("push includes obsolete changeset: %s!")
             mst = "push includes %s changeset: %s!"
             # plain versions for i18n tool to detect them
             _("push includes unstable changeset: %s!")
             _("push includes bumped changeset: %s!")
             _("push includes divergent changeset: %s!")
             # If we are to push if there is at least one
             # obsolete or unstable changeset in missing, at
             # least one of the missinghead will be obsolete or
             # unstable. So checking heads only is ok
             for node in outgoing.missingheads:
                 ctx = unfi[node]
                 if ctx.obsolete():
                     raise util.Abort(mso % ctx)
                 elif ctx.troubled():
                     raise util.Abort(_(mst)
                                      % (ctx.troubles()[0],
                                         ctx))
         newbm = pushop.ui.configlist('bookmarks', 'pushing')
         discovery.checkheads(unfi, pushop.remote, outgoing,
                              pushop.remoteheads,
                              pushop.newbranch,
                              bool(pushop.incoming),
                              newbm)
     return True
 
 def _pushbundle2(pushop):
     """push data to the remote using bundle2
 
     The only currently supported type of data is changegroup but this will
     evolve in the future."""
     # Send known head to the server for race detection.
     capsblob = urllib.unquote(pushop.remote.capable('bundle2-exp'))
     caps = bundle2.decodecaps(capsblob)
     bundler = bundle2.bundle20(pushop.ui, caps)
     # create reply capability
     capsblob = bundle2.encodecaps(pushop.repo.bundle2caps)
     bundler.addpart(bundle2.bundlepart('b2x:replycaps', data=capsblob))
     if not pushop.force:
         part = bundle2.bundlepart('B2X:CHECK:HEADS',
                                   data=iter(pushop.remoteheads))
         bundler.addpart(part)
+    extrainfo = _pushbundle2extraparts(pushop, bundler)
     # add the changegroup bundle
     cg = changegroup.getlocalbundle(pushop.repo, 'push', pushop.outgoing)
     cgpart = bundle2.bundlepart('B2X:CHANGEGROUP', data=cg.getchunks())
     bundler.addpart(cgpart)
     stream = util.chunkbuffer(bundler.getchunks())
     reply = pushop.remote.unbundle(stream, ['force'], 'push')
     try:
         op = bundle2.processbundle(pushop.repo, reply)
     except KeyError, exc:
         raise util.Abort('missing support for %s' % exc)
     cgreplies = op.records.getreplies(cgpart.id)
     assert len(cgreplies['changegroup']) == 1
     pushop.ret = cgreplies['changegroup'][0]['return']
+    _pushbundle2extrareply(pushop, op, extrainfo)
+
+def _pushbundle2extraparts(pushop, bundler):
+    """hook function to let extensions add parts
+
+    Return a dict to let extensions pass data to the reply processing.
+    """
+    return {}
+
+def _pushbundle2extrareply(pushop, op, extrainfo):
+    """hook function to let extensions react to part replies
+
+    The dict from _pushbundle2extrareply is fed to this function.
+    """
+    pass
 
 def _pushchangeset(pushop):
     """Make the actual push of changeset bundle to remote repo"""
     outgoing = pushop.outgoing
     unbundle = pushop.remote.capable('unbundle')
     # TODO: get bundlecaps from remote
     bundlecaps = None
     # create a changegroup from local
     if pushop.revs is None and not (outgoing.excluded
                             or pushop.repo.changelog.filteredrevs):
         # push everything,
         # use the fast path, no race possible on push
         bundler = changegroup.bundle10(pushop.repo, bundlecaps)
         cg = changegroup.getsubset(pushop.repo,
                                    outgoing,
                                    bundler,
                                    'push',
                                    fastpath=True)
     else:
         cg = changegroup.getlocalbundle(pushop.repo, 'push', outgoing,
                                         bundlecaps)
 
     # apply changegroup to remote
     if unbundle:
         # local repo finds heads on server, finds out what
         # revs it must push. once revs transferred, if server
         # finds it has different heads (someone else won
         # commit/push race), server aborts.
         if pushop.force:
             remoteheads = ['force']
         else:
             remoteheads = pushop.remoteheads
         # ssh: return remote's addchangegroup()
         # http: return remote's addchangegroup() or 0 for error
         pushop.ret = pushop.remote.unbundle(cg, remoteheads,
                                             'push')
     else:
         # we return an integer indicating remote head count
         # change
         pushop.ret = pushop.remote.addchangegroup(cg, 'push', pushop.repo.url())
 
 def _pushcomputecommonheads(pushop):
     unfi = pushop.repo.unfiltered()
     if pushop.ret:
         # push succeed, synchronize target of the push
         cheads = pushop.outgoing.missingheads
     elif pushop.revs is None:
         # All out push fails. synchronize all common
         cheads = pushop.outgoing.commonheads
     else:
         # I want cheads = heads(::missingheads and ::commonheads)
         # (missingheads is revs with secret changeset filtered out)
         #
         # This can be expressed as:
         #     cheads = ( (missingheads and ::commonheads)
         #              + (commonheads and ::missingheads))"
         #              )
         #
         # while trying to push we already computed the following:
         #     common = (::commonheads)
         #     missing = ((commonheads::missingheads) - commonheads)
         #
         # We can pick:
         # * missingheads part of common (::commonheads)
         common = set(pushop.outgoing.common)
         nm = pushop.repo.changelog.nodemap
         cheads = [node for node in pushop.revs if nm[node] in common]
         # and
         # * commonheads parents on missing
         revset = unfi.set('%ln and parents(roots(%ln))',
                          pushop.outgoing.commonheads,
                          pushop.outgoing.missing)
         cheads.extend(c.node() for c in revset)
     pushop.commonheads = cheads
 
 def _pushsyncphase(pushop):
     """synchronise phase information locally and remotely"""
     unfi = pushop.repo.unfiltered()
     cheads = pushop.commonheads
     if pushop.ret:
         # push succeed, synchronize target of the push
         cheads = pushop.outgoing.missingheads
     elif pushop.revs is None:
         # All out push fails. synchronize all common
         cheads = pushop.outgoing.commonheads
     else:
         # I want cheads = heads(::missingheads and ::commonheads)
         # (missingheads is revs with secret changeset filtered out)
         #
         # This can be expressed as:
         #     cheads = ( (missingheads and ::commonheads)
         #              + (commonheads and ::missingheads))"
         #              )
         #
         # while trying to push we already computed the following:
         #     common = (::commonheads)
         #     missing = ((commonheads::missingheads) - commonheads)
         #
         # We can pick:
         # * missingheads part of common (::commonheads)
         common = set(pushop.outgoing.common)
         nm = pushop.repo.changelog.nodemap
         cheads = [node for node in pushop.revs if nm[node] in common]
         # and
         # * commonheads parents on missing
         revset = unfi.set('%ln and parents(roots(%ln))',
                          pushop.outgoing.commonheads,
                          pushop.outgoing.missing)
         cheads.extend(c.node() for c in revset)
     pushop.commonheads = cheads
     # even when we don't push, exchanging phase data is useful
     remotephases = pushop.remote.listkeys('phases')
     if (pushop.ui.configbool('ui', '_usedassubrepo', False)
         and remotephases    # server supports phases
         and pushop.ret is None # nothing was pushed
         and remotephases.get('publishing', False)):
         # When:
         # - this is a subrepo push
         # - and remote support phase
         # - and no changeset was pushed
         # - and remote is publishing
         # We may be in issue 3871 case!
         # We drop the possible phase synchronisation done by
         # courtesy to publish changesets possibly locally draft
         # on the remote.
         remotephases = {'publishing': 'True'}
     if not remotephases: # old server or public only reply from non-publishing
         _localphasemove(pushop, cheads)
         # don't push any phase data as there is nothing to push
     else:
         ana = phases.analyzeremotephases(pushop.repo, cheads,
                                          remotephases)
         pheads, droots = ana
         ### Apply remote phase on local
         if remotephases.get('publishing', False):
             _localphasemove(pushop, cheads)
         else: # publish = False
             _localphasemove(pushop, pheads)
             _localphasemove(pushop, cheads, phases.draft)
         ### Apply local phase on remote
 
         # Get the list of all revs draft on remote by public here.
         # XXX Beware that revset break if droots is not strictly
         # XXX root we may want to ensure it is but it is costly
         outdated =  unfi.set('heads((%ln::%ln) and public())',
                              droots, cheads)
         for newremotehead in outdated:
             r = pushop.remote.pushkey('phases',
                                       newremotehead.hex(),
                                       str(phases.draft),
                                       str(phases.public))
             if not r:
                 pushop.ui.warn(_('updating %s to public failed!\n')
                                        % newremotehead)
 
 def _localphasemove(pushop, nodes, phase=phases.public):
     """move <nodes> to <phase> in the local source repo"""
     if pushop.locallocked:
         phases.advanceboundary(pushop.repo, phase, nodes)
     else:
         # repo is not locked, do not change any phases!
         # Informs the user that phases should have been moved when
         # applicable.
         actualmoves = [n for n in nodes if phase < pushop.repo[n].phase()]
         phasestr = phases.phasenames[phase]
         if actualmoves:
             pushop.ui.status(_('cannot lock source repo, skipping '
                                'local %s phase update\n') % phasestr)
 
 def _pushobsolete(pushop):
     """utility function to push obsolete markers to a remote"""
     pushop.ui.debug('try to push obsolete markers to remote\n')
     repo = pushop.repo
     remote = pushop.remote
     if (obsolete._enabled and repo.obsstore and
         'obsolete' in remote.listkeys('namespaces')):
         rslts = []
         remotedata = repo.listkeys('obsolete')
         for key in sorted(remotedata, reverse=True):
             # reverse sort to ensure we end with dump0
             data = remotedata[key]
             rslts.append(remote.pushkey('obsolete', key, '', data))
         if [r for r in rslts if not r]:
             msg = _('failed to push some obsolete markers!\n')
             repo.ui.warn(msg)
 
 def _pushbookmark(pushop):
     """Update bookmark position on remote"""
     ui = pushop.ui
     repo = pushop.repo.unfiltered()
     remote = pushop.remote
     ui.debug("checking for updated bookmarks\n")
     revnums = map(repo.changelog.rev, pushop.revs or [])
     ancestors = [a for a in repo.changelog.ancestors(revnums, inclusive=True)]
     (addsrc, adddst, advsrc, advdst, diverge, differ, invalid
      ) = bookmarks.compare(repo, repo._bookmarks, remote.listkeys('bookmarks'),
                            srchex=hex)
 
     for b, scid, dcid in advsrc:
         if ancestors and repo[scid].rev() not in ancestors:
             continue
         if remote.pushkey('bookmarks', b, dcid, scid):
             ui.status(_("updating bookmark %s\n") % b)
         else:
             ui.warn(_('updating bookmark %s failed!\n') % b)
 
 class pulloperation(object):
     """A object that represent a single pull operation
 
     It purpose is to carry push related state and very common operation.
 
     A new should be created at the beginning of each pull and discarded
     afterward.
     """
 
     def __init__(self, repo, remote, heads=None, force=False):
         # repo we pull into
         self.repo = repo
         # repo we pull from
         self.remote = remote
         # revision we try to pull (None is "all")
         self.heads = heads
         # do we force pull?
         self.force = force
         # the name the pull transaction
         self._trname = 'pull\n' + util.hidepassword(remote.url())
         # hold the transaction once created
         self._tr = None
         # set of common changeset between local and remote before pull
         self.common = None
         # set of pulled head
         self.rheads = None
         # list of missing changeset to fetch remotely
         self.fetch = None
         # result of changegroup pulling (used as return code by pull)
         self.cgresult = None
         # list of step remaining todo (related to future bundle2 usage)
         self.todosteps = set(['changegroup', 'phases', 'obsmarkers'])
 
     @util.propertycache
     def pulledsubset(self):
         """heads of the set of changeset target by the pull"""
         # compute target subset
         if self.heads is None:
             # We pulled every thing possible
             # sync on everything common
             c = set(self.common)
             ret = list(self.common)
             for n in self.rheads:
                 if n not in c:
                     ret.append(n)
             return ret
         else:
             # We pulled a specific subset
             # sync on this subset
             return self.heads
 
     def gettransaction(self):
         """get appropriate pull transaction, creating it if needed"""
         if self._tr is None:
             self._tr = self.repo.transaction(self._trname)
         return self._tr
 
     def closetransaction(self):
         """close transaction if created"""
         if self._tr is not None:
             self._tr.close()
 
     def releasetransaction(self):
         """release transaction if created"""
         if self._tr is not None:
             self._tr.release()
 
 def pull(repo, remote, heads=None, force=False):
     pullop = pulloperation(repo, remote, heads, force)
     if pullop.remote.local():
         missing = set(pullop.remote.requirements) - pullop.repo.supported
         if missing:
             msg = _("required features are not"
                     " supported in the destination:"
                     " %s") % (', '.join(sorted(missing)))
             raise util.Abort(msg)
 
     lock = pullop.repo.lock()
     try:
         _pulldiscovery(pullop)
         if (pullop.repo.ui.configbool('server', 'bundle2', False)
             and pullop.remote.capable('bundle2-exp')):
             _pullbundle2(pullop)
         if 'changegroup' in pullop.todosteps:
             _pullchangeset(pullop)
         if 'phases' in pullop.todosteps:
             _pullphase(pullop)
         if 'obsmarkers' in pullop.todosteps:
             _pullobsolete(pullop)
         pullop.closetransaction()
     finally:
         pullop.releasetransaction()
         lock.release()
 
     return pullop.cgresult
 
 def _pulldiscovery(pullop):
     """discovery phase for the pull
 
     Current handle changeset discovery only, will change handle all discovery
     at some point."""
     tmp = discovery.findcommonincoming(pullop.repo.unfiltered(),
                                        pullop.remote,
                                        heads=pullop.heads,
                                        force=pullop.force)
     pullop.common, pullop.fetch, pullop.rheads = tmp
 
 def _pullbundle2(pullop):
     """pull data using bundle2
 
     For now, the only supported data are changegroup."""
     kwargs = {'bundlecaps': set(['HG2X'])}
     capsblob = bundle2.encodecaps(pullop.repo.bundle2caps)
     kwargs['bundlecaps'].add('bundle2=' + urllib.quote(capsblob))
     # pulling changegroup
     pullop.todosteps.remove('changegroup')
     if not pullop.fetch:
             pullop.repo.ui.status(_("no changes found\n"))
             pullop.cgresult = 0
     else:
         kwargs['common'] = pullop.common
         kwargs['heads'] = pullop.heads or pullop.rheads
         if pullop.heads is None and list(pullop.common) == [nullid]:
             pullop.repo.ui.status(_("requesting all changes\n"))
     if kwargs.keys() == ['format']:
         return # nothing to pull
     bundle = pullop.remote.getbundle('pull', **kwargs)
     try:
         op = bundle2.processbundle(pullop.repo, bundle, pullop.gettransaction)
     except KeyError, exc:
         raise util.Abort('missing support for %s' % exc)
     assert len(op.records['changegroup']) == 1
     pullop.cgresult = op.records['changegroup'][0]['return']
 
 def _pullchangeset(pullop):
     """pull changeset from unbundle into the local repo"""
     # We delay the open of the transaction as late as possible so we
     # don't open transaction for nothing or you break future useful
     # rollback call
     pullop.todosteps.remove('changegroup')
     if not pullop.fetch:
             pullop.repo.ui.status(_("no changes found\n"))
             pullop.cgresult = 0
             return
     pullop.gettransaction()
     if pullop.heads is None and list(pullop.common) == [nullid]:
         pullop.repo.ui.status(_("requesting all changes\n"))
     elif pullop.heads is None and pullop.remote.capable('changegroupsubset'):
         # issue1320, avoid a race if remote changed after discovery
         pullop.heads = pullop.rheads
 
     if pullop.remote.capable('getbundle'):
         # TODO: get bundlecaps from remote
         cg = pullop.remote.getbundle('pull', common=pullop.common,
                                      heads=pullop.heads or pullop.rheads)
     elif pullop.heads is None:
         cg = pullop.remote.changegroup(pullop.fetch, 'pull')
     elif not pullop.remote.capable('changegroupsubset'):
         raise util.Abort(_("partial pull cannot be done because "
                                    "other repository doesn't support "
                                    "changegroupsubset."))
     else:
         cg = pullop.remote.changegroupsubset(pullop.fetch, pullop.heads, 'pull')
     pullop.cgresult = changegroup.addchangegroup(pullop.repo, cg, 'pull',
                                                  pullop.remote.url())
 
 def _pullphase(pullop):
     # Get remote phases data from remote
     pullop.todosteps.remove('phases')
     remotephases = pullop.remote.listkeys('phases')
     publishing = bool(remotephases.get('publishing', False))
     if remotephases and not publishing:
         # remote is new and unpublishing
         pheads, _dr = phases.analyzeremotephases(pullop.repo,
                                                  pullop.pulledsubset,
                                                  remotephases)
         phases.advanceboundary(pullop.repo, phases.public, pheads)
         phases.advanceboundary(pullop.repo, phases.draft,
                                pullop.pulledsubset)
     else:
         # Remote is old or publishing all common changesets
         # should be seen as public
         phases.advanceboundary(pullop.repo, phases.public,
                                pullop.pulledsubset)
 
 def _pullobsolete(pullop):
     """utility function to pull obsolete markers from a remote
 
     The `gettransaction` is function that return the pull transaction, creating
     one if necessary. We return the transaction to inform the calling code that
     a new transaction have been created (when applicable).
 
     Exists mostly to allow overriding for experimentation purpose"""
     pullop.todosteps.remove('obsmarkers')
     tr = None
     if obsolete._enabled:
         pullop.repo.ui.debug('fetching remote obsolete markers\n')
         remoteobs = pullop.remote.listkeys('obsolete')
         if 'dump0' in remoteobs:
             tr = pullop.gettransaction()
             for key in sorted(remoteobs, reverse=True):
                 if key.startswith('dump'):
                     data = base85.b85decode(remoteobs[key])
                     pullop.repo.obsstore.mergemarkers(tr, data)
             pullop.repo.invalidatevolatilesets()
     return tr
 
 def getbundle(repo, source, heads=None, common=None, bundlecaps=None):
     """return a full bundle (with potentially multiple kind of parts)
 
     Could be a bundle HG10 or a bundle HG2X depending on bundlecaps
     passed. For now, the bundle can contain only changegroup, but this will
     changes when more part type will be available for bundle2.
 
     This is different from changegroup.getbundle that only returns an HG10
     changegroup bundle. They may eventually get reunited in the future when we
     have a clearer idea of the API we what to query different data.
 
     The implementation is at a very early stage and will get massive rework
     when the API of bundle is refined.
     """
     # build bundle here.
     cg = changegroup.getbundle(repo, source, heads=heads,
                                common=common, bundlecaps=bundlecaps)
     if bundlecaps is None or 'HG2X' not in bundlecaps:
         return cg
     # very crude first implementation,
     # the bundle API will change and the generation will be done lazily.
     b2caps = {}
     for bcaps in bundlecaps:
         if bcaps.startswith('bundle2='):
             blob = urllib.unquote(bcaps[len('bundle2='):])
             b2caps.update(bundle2.decodecaps(blob))
     bundler = bundle2.bundle20(repo.ui, b2caps)
     part = bundle2.bundlepart('b2x:changegroup', data=cg.getchunks())
     bundler.addpart(part)
     return util.chunkbuffer(bundler.getchunks())
 
 class PushRaced(RuntimeError):
     """An exception raised during unbundling that indicate a push race"""
 
 def check_heads(repo, their_heads, context):
     """check if the heads of a repo have been modified
 
     Used by peer for unbundling.
     """
     heads = repo.heads()
     heads_hash = util.sha1(''.join(sorted(heads))).digest()
     if not (their_heads == ['force'] or their_heads == heads or
             their_heads == ['hashed', heads_hash]):
         # someone else committed/pushed/unbundled while we
         # were transferring data
         raise PushRaced('repository changed while %s - '
                         'please try again' % context)
 
 def unbundle(repo, cg, heads, source, url):
     """Apply a bundle to a repo.
 
     this function makes sure the repo is locked during the application and have
     mechanism to check that no push race occurred between the creation of the
     bundle and its application.
 
     If the push was raced as PushRaced exception is raised."""
     r = 0
     # need a transaction when processing a bundle2 stream
     tr = None
     lock = repo.lock()
     try:
         check_heads(repo, heads, 'uploading changes')
         # push can proceed
         if util.safehasattr(cg, 'params'):
             tr = repo.transaction('unbundle')
             r = bundle2.processbundle(repo, cg, lambda: tr).reply
             tr.close()
         else:
             r = changegroup.addchangegroup(repo, cg, source, url)
     finally:
         if tr is not None:
             tr.release()
         lock.release()
     return r