push: move obsolescence marker exchange in the exchange module

The obsolescence marker exchange code was already extracted during a previous
cycle. We are moving the extracted functio in this module. This function will
read and write data in the `pushoperation` object and I prefer to have all core
function collaborating through this object in the same place.

This changeset is pure code movement only. Code change for direct consumption of
the `pushoperation` object will come later.

mercurial/exchange.py

@@ -1,279 +1,295
 # exchange.py - utily to exchange data between repo.
 #
 # 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
 import errno
 import util, scmutil, changegroup
 import discovery, phases, obsolete, bookmarks
 
 
 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 begining 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
 
 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"))
     unfi = pushop.repo.unfiltered()
     def localphasemove(nodes, phase=phases.public):
         """move <nodes> to <phase> in the local source repo"""
         if locallock is not None:
             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)
     # get local lock as we might write phase data
     locallock = None
     try:
         locallock = pushop.repo.lock()
     except IOError, err:
         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.force, pushop.revs)
         lock = None
         unbundle = pushop.remote.capable('unbundle')
         if not unbundle:
             lock = pushop.remote.lock()
         try:
             # discovery
             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)
 
 
             if not outgoing.missing:
                 # nothing to push
                 scmutil.nochangesfound(unfi.ui, unfi, outgoing.excluded)
                 ret = None
             else:
                 # 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,
                                          remoteheads, pushop.newbranch,
                                          bool(inc), newbm)
 
                 # 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 = pushop.repo._changegroupsubset(outgoing,
                                                         bundler,
                                                         'push',
                                                         fastpath=True)
                 else:
                     cg = pushop.repo.getlocalbundle('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']
                     # ssh: return remote's addchangegroup()
                     # http: return remote's addchangegroup() or 0 for error
                     ret = pushop.remote.unbundle(cg, remoteheads, 'push')
                 else:
                     # we return an integer indicating remote head count
                     # change
                     ret = pushop.remote.addchangegroup(cg, 'push',
                                                        pushop.repo.url())
 
             if ret:
                 # push succeed, synchronize target of the push
                 cheads = outgoing.missingheads
             elif pushop.revs is None:
                 # All out push fails. synchronize all common
                 cheads = 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(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))',
                                  outgoing.commonheads,
                                  outgoing.missing)
                 cheads.extend(c.node() for c in revset)
             # 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 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 repo
                 localphasemove(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(cheads)
                 else: # publish = False
                     localphasemove(pheads)
                     localphasemove(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)
             pushop.ui.debug('try to push obsolete markers to remote\n')
-            obsolete.syncpush(pushop.repo, pushop.remote)
+            _pushobsolete(pushop.repo, pushop.remote)
         finally:
             if lock is not None:
                 lock.release()
     finally:
         if locallock is not None:
             locallock.release()
 
     _pushbookmark(pushop)
     return ret
 
+def _pushobsolete(repo, remote):
+    """utility function to push obsolete markers to a remote
+
+    Exist mostly to allow overriding for experimentation purpose"""
+    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)

mercurial/obsolete.py

@@ -1,880 +1,864
 # obsolete.py - obsolete markers handling
 #
 # Copyright 2012 Pierre-Yves David <[e-mail]>
 #                Logilab SA        <[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.
 
 """Obsolete markers handling
 
 An obsolete marker maps an old changeset to a list of new
 changesets. If the list of new changesets is empty, the old changeset
 is said to be "killed". Otherwise, the old changeset is being
 "replaced" by the new changesets.
 
 Obsolete markers can be used to record and distribute changeset graph
 transformations performed by history rewriting operations, and help
 building new tools to reconciliate conflicting rewriting actions. To
 facilitate conflicts resolution, markers include various annotations
 besides old and news changeset identifiers, such as creation date or
 author name.
 
 The old obsoleted changeset is called "precursor" and possible replacements are
 called "successors".  Markers that used changeset X as a precursors are called
 "successor markers of X" because they hold information about the successors of
 X. Markers that use changeset Y as a successors are call "precursor markers of
 Y" because they hold information about the precursors of Y.
 
 Examples:
 
 - When changeset A is replacement by a changeset A', one marker is stored:
 
     (A, (A'))
 
 - When changesets A and B are folded into a new changeset C two markers are
   stored:
 
     (A, (C,)) and (B, (C,))
 
 - When changeset A is simply "pruned" from the graph, a marker in create:
 
     (A, ())
 
 - When changeset A is split into B and C, a single marker are used:
 
     (A, (C, C))
 
   We use a single marker to distinct the "split" case from the "divergence"
   case. If two independents operation rewrite the same changeset A in to A' and
   A'' when have an error case: divergent rewriting. We can detect it because
   two markers will be created independently:
 
   (A, (B,)) and (A, (C,))
 
 Format
 ------
 
 Markers are stored in an append-only file stored in
 '.hg/store/obsstore'.
 
 The file starts with a version header:
 
 - 1 unsigned byte: version number, starting at zero.
 
 
 The header is followed by the markers. Each marker is made of:
 
 - 1 unsigned byte: number of new changesets "R", could be zero.
 
 - 1 unsigned 32-bits integer: metadata size "M" in bytes.
 
 - 1 byte: a bit field. It is reserved for flags used in obsolete
   markers common operations, to avoid repeated decoding of metadata
   entries.
 
 - 20 bytes: obsoleted changeset identifier.
 
 - N*20 bytes: new changesets identifiers.
 
 - M bytes: metadata as a sequence of nul-terminated strings. Each
   string contains a key and a value, separated by a color ':', without
   additional encoding. Keys cannot contain '\0' or ':' and values
   cannot contain '\0'.
 """
 import struct
 import util, base85, node
 import phases
 from i18n import _
 
 _pack = struct.pack
 _unpack = struct.unpack
 
 _SEEK_END = 2 # os.SEEK_END was introduced in Python 2.5
 
 # the obsolete feature is not mature enough to be enabled by default.
 # you have to rely on third party extension extension to enable this.
 _enabled = False
 
 # data used for parsing and writing
 _fmversion = 0
 _fmfixed   = '>BIB20s'
 _fmnode = '20s'
 _fmfsize = struct.calcsize(_fmfixed)
 _fnodesize = struct.calcsize(_fmnode)
 
 ### obsolescence marker flag
 
 ## bumpedfix flag
 #
 # When a changeset A' succeed to a changeset A which became public, we call A'
 # "bumped" because it's a successors of a public changesets
 #
 # o    A' (bumped)
 # |`:
 # | o  A
 # |/
 # o    Z
 #
 # The way to solve this situation is to create a new changeset Ad as children
 # of A. This changeset have the same content than A'. So the diff from A to A'
 # is the same than the diff from A to Ad. Ad is marked as a successors of A'
 #
 # o   Ad
 # |`:
 # | x A'
 # |'|
 # o | A
 # |/
 # o Z
 #
 # But by transitivity Ad is also a successors of A. To avoid having Ad marked
 # as bumped too, we add the `bumpedfix` flag to the marker. <A', (Ad,)>.
 # This flag mean that the successors express the changes between the public and
 # bumped version and fix the situation, breaking the transitivity of
 # "bumped" here.
 bumpedfix = 1
 
 def _readmarkers(data):
     """Read and enumerate markers from raw data"""
     off = 0
     diskversion = _unpack('>B', data[off:off + 1])[0]
     off += 1
     if diskversion != _fmversion:
         raise util.Abort(_('parsing obsolete marker: unknown version %r')
                          % diskversion)
 
     # Loop on markers
     l = len(data)
     while off + _fmfsize <= l:
         # read fixed part
         cur = data[off:off + _fmfsize]
         off += _fmfsize
         nbsuc, mdsize, flags, pre = _unpack(_fmfixed, cur)
         # read replacement
         sucs = ()
         if nbsuc:
             s = (_fnodesize * nbsuc)
             cur = data[off:off + s]
             sucs = _unpack(_fmnode * nbsuc, cur)
             off += s
         # read metadata
         # (metadata will be decoded on demand)
         metadata = data[off:off + mdsize]
         if len(metadata) != mdsize:
             raise util.Abort(_('parsing obsolete marker: metadata is too '
                                'short, %d bytes expected, got %d')
                              % (mdsize, len(metadata)))
         off += mdsize
         yield (pre, sucs, flags, metadata)
 
 def encodemeta(meta):
     """Return encoded metadata string to string mapping.
 
     Assume no ':' in key and no '\0' in both key and value."""
     for key, value in meta.iteritems():
         if ':' in key or '\0' in key:
             raise ValueError("':' and '\0' are forbidden in metadata key'")
         if '\0' in value:
             raise ValueError("':' are forbidden in metadata value'")
     return '\0'.join(['%s:%s' % (k, meta[k]) for k in sorted(meta)])
 
 def decodemeta(data):
     """Return string to string dictionary from encoded version."""
     d = {}
     for l in data.split('\0'):
         if l:
             key, value = l.split(':')
             d[key] = value
     return d
 
 class marker(object):
     """Wrap obsolete marker raw data"""
 
     def __init__(self, repo, data):
         # the repo argument will be used to create changectx in later version
         self._repo = repo
         self._data = data
         self._decodedmeta = None
 
     def __hash__(self):
         return hash(self._data)
 
     def __eq__(self, other):
         if type(other) != type(self):
             return False
         return self._data == other._data
 
     def precnode(self):
         """Precursor changeset node identifier"""
         return self._data[0]
 
     def succnodes(self):
         """List of successor changesets node identifiers"""
         return self._data[1]
 
     def metadata(self):
         """Decoded metadata dictionary"""
         if self._decodedmeta is None:
             self._decodedmeta = decodemeta(self._data[3])
         return self._decodedmeta
 
     def date(self):
         """Creation date as (unixtime, offset)"""
         parts = self.metadata()['date'].split(' ')
         return (float(parts[0]), int(parts[1]))
 
 class obsstore(object):
     """Store obsolete markers
 
     Markers can be accessed with two mappings:
     - precursors[x] -> set(markers on precursors edges of x)
     - successors[x] -> set(markers on successors edges of x)
     """
 
     def __init__(self, sopener):
         # caches for various obsolescence related cache
         self.caches = {}
         self._all = []
         # new markers to serialize
         self.precursors = {}
         self.successors = {}
         self.sopener = sopener
         data = sopener.tryread('obsstore')
         if data:
             self._load(_readmarkers(data))
 
     def __iter__(self):
         return iter(self._all)
 
     def __nonzero__(self):
         return bool(self._all)
 
     def create(self, transaction, prec, succs=(), flag=0, metadata=None):
         """obsolete: add a new obsolete marker
 
         * ensuring it is hashable
         * check mandatory metadata
         * encode metadata
         """
         if metadata is None:
             metadata = {}
         if 'date' not in metadata:
             metadata['date'] = "%d %d" % util.makedate()
         if len(prec) != 20:
             raise ValueError(prec)
         for succ in succs:
             if len(succ) != 20:
                 raise ValueError(succ)
         marker = (str(prec), tuple(succs), int(flag), encodemeta(metadata))
         self.add(transaction, [marker])
 
     def add(self, transaction, markers):
         """Add new markers to the store
 
         Take care of filtering duplicate.
         Return the number of new marker."""
         if not _enabled:
             raise util.Abort('obsolete feature is not enabled on this repo')
         known = set(self._all)
         new = []
         for m in markers:
             if m not in known:
                 known.add(m)
                 new.append(m)
         if new:
             f = self.sopener('obsstore', 'ab')
             try:
                 # Whether the file's current position is at the begin or at
                 # the end after opening a file for appending is implementation
                 # defined. So we must seek to the end before calling tell(),
                 # or we may get a zero offset for non-zero sized files on
                 # some platforms (issue3543).
                 f.seek(0, _SEEK_END)
                 offset = f.tell()
                 transaction.add('obsstore', offset)
                 # offset == 0: new file - add the version header
                 for bytes in _encodemarkers(new, offset == 0):
                     f.write(bytes)
             finally:
                 # XXX: f.close() == filecache invalidation == obsstore rebuilt.
                 # call 'filecacheentry.refresh()'  here
                 f.close()
             self._load(new)
             # new marker *may* have changed several set. invalidate the cache.
             self.caches.clear()
         return len(new)
 
     def mergemarkers(self, transaction, data):
         markers = _readmarkers(data)
         self.add(transaction, markers)
 
     def _load(self, markers):
         for mark in markers:
             self._all.append(mark)
             pre, sucs = mark[:2]
             self.successors.setdefault(pre, set()).add(mark)
             for suc in sucs:
                 self.precursors.setdefault(suc, set()).add(mark)
         if node.nullid in self.precursors:
             raise util.Abort(_('bad obsolescence marker detected: '
                                'invalid successors nullid'))
 
 def _encodemarkers(markers, addheader=False):
     # Kept separate from flushmarkers(), it will be reused for
     # markers exchange.
     if addheader:
         yield _pack('>B', _fmversion)
     for marker in markers:
         yield _encodeonemarker(marker)
 
 
 def _encodeonemarker(marker):
     pre, sucs, flags, metadata = marker
     nbsuc = len(sucs)
     format = _fmfixed + (_fmnode * nbsuc)
     data = [nbsuc, len(metadata), flags, pre]
     data.extend(sucs)
     return _pack(format, *data) + metadata
 
 # arbitrary picked to fit into 8K limit from HTTP server
 # you have to take in account:
 # - the version header
 # - the base85 encoding
 _maxpayload = 5300
 
 def listmarkers(repo):
     """List markers over pushkey"""
     if not repo.obsstore:
         return {}
     keys = {}
     parts = []
     currentlen = _maxpayload * 2  # ensure we create a new part
     for marker in  repo.obsstore:
         nextdata = _encodeonemarker(marker)
         if (len(nextdata) + currentlen > _maxpayload):
             currentpart = []
             currentlen = 0
             parts.append(currentpart)
         currentpart.append(nextdata)
         currentlen += len(nextdata)
     for idx, part in enumerate(reversed(parts)):
         data = ''.join([_pack('>B', _fmversion)] + part)
         keys['dump%i' % idx] = base85.b85encode(data)
     return keys
 
 def pushmarker(repo, key, old, new):
     """Push markers over pushkey"""
     if not key.startswith('dump'):
         repo.ui.warn(_('unknown key: %r') % key)
         return 0
     if old:
         repo.ui.warn(_('unexpected old value') % key)
         return 0
     data = base85.b85decode(new)
     lock = repo.lock()
     try:
         tr = repo.transaction('pushkey: obsolete markers')
         try:
             repo.obsstore.mergemarkers(tr, data)
             tr.close()
             return 1
         finally:
             tr.release()
     finally:
         lock.release()
 
-def syncpush(repo, remote):
-    """utility function to push obsolete markers to a remote
-
-    Exist mostly to allow overriding for experimentation purpose"""
-    if (_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 syncpull(repo, remote, gettransaction):
     """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"""
     tr = None
     if _enabled:
         repo.ui.debug('fetching remote obsolete markers\n')
         remoteobs = remote.listkeys('obsolete')
         if 'dump0' in remoteobs:
             tr = gettransaction()
             for key in sorted(remoteobs, reverse=True):
                 if key.startswith('dump'):
                     data = base85.b85decode(remoteobs[key])
                     repo.obsstore.mergemarkers(tr, data)
             repo.invalidatevolatilesets()
     return tr
 
 def allmarkers(repo):
     """all obsolete markers known in a repository"""
     for markerdata in repo.obsstore:
         yield marker(repo, markerdata)
 
 def precursormarkers(ctx):
     """obsolete marker marking this changeset as a successors"""
     for data in ctx._repo.obsstore.precursors.get(ctx.node(), ()):
         yield marker(ctx._repo, data)
 
 def successormarkers(ctx):
     """obsolete marker making this changeset obsolete"""
     for data in ctx._repo.obsstore.successors.get(ctx.node(), ()):
         yield marker(ctx._repo, data)
 
 def allsuccessors(obsstore, nodes, ignoreflags=0):
     """Yield node for every successor of <nodes>.
 
     Some successors may be unknown locally.
 
     This is a linear yield unsuited to detecting split changesets. It includes
     initial nodes too."""
     remaining = set(nodes)
     seen = set(remaining)
     while remaining:
         current = remaining.pop()
         yield current
         for mark in obsstore.successors.get(current, ()):
             # ignore marker flagged with specified flag
             if mark[2] & ignoreflags:
                 continue
             for suc in mark[1]:
                 if suc not in seen:
                     seen.add(suc)
                     remaining.add(suc)
 
 def allprecursors(obsstore, nodes, ignoreflags=0):
     """Yield node for every precursors of <nodes>.
 
     Some precursors may be unknown locally.
 
     This is a linear yield unsuited to detecting folded changesets. It includes
     initial nodes too."""
 
     remaining = set(nodes)
     seen = set(remaining)
     while remaining:
         current = remaining.pop()
         yield current
         for mark in obsstore.precursors.get(current, ()):
             # ignore marker flagged with specified flag
             if mark[2] & ignoreflags:
                 continue
             suc = mark[0]
             if suc not in seen:
                 seen.add(suc)
                 remaining.add(suc)
 
 def foreground(repo, nodes):
     """return all nodes in the "foreground" of other node
 
     The foreground of a revision is anything reachable using parent -> children
     or precursor -> successor relation. It is very similar to "descendant" but
     augmented with obsolescence information.
 
     Beware that possible obsolescence cycle may result if complex situation.
     """
     repo = repo.unfiltered()
     foreground = set(repo.set('%ln::', nodes))
     if repo.obsstore:
         # We only need this complicated logic if there is obsolescence
         # XXX will probably deserve an optimised revset.
         nm = repo.changelog.nodemap
         plen = -1
         # compute the whole set of successors or descendants
         while len(foreground) != plen:
             plen = len(foreground)
             succs = set(c.node() for c in foreground)
             mutable = [c.node() for c in foreground if c.mutable()]
             succs.update(allsuccessors(repo.obsstore, mutable))
             known = (n for n in succs if n in nm)
             foreground = set(repo.set('%ln::', known))
     return set(c.node() for c in foreground)
 
 
 def successorssets(repo, initialnode, cache=None):
     """Return all set of successors of initial nodes
 
     The successors set of a changeset A are a group of revisions that succeed
     A. It succeeds A as a consistent whole, each revision being only a partial
     replacement. The successors set contains non-obsolete changesets only.
 
     This function returns the full list of successor sets which is why it
     returns a list of tuples and not just a single tuple. Each tuple is a valid
     successors set. Not that (A,) may be a valid successors set for changeset A
     (see below).
 
     In most cases, a changeset A will have a single element (e.g. the changeset
     A is replaced by A') in its successors set. Though, it is also common for a
     changeset A to have no elements in its successor set (e.g. the changeset
     has been pruned). Therefore, the returned list of successors sets will be
     [(A',)] or [], respectively.
 
     When a changeset A is split into A' and B', however, it will result in a
     successors set containing more than a single element, i.e. [(A',B')].
     Divergent changesets will result in multiple successors sets, i.e. [(A',),
     (A'')].
 
     If a changeset A is not obsolete, then it will conceptually have no
     successors set. To distinguish this from a pruned changeset, the successor
     set will only contain itself, i.e. [(A,)].
 
     Finally, successors unknown locally are considered to be pruned (obsoleted
     without any successors).
 
     The optional `cache` parameter is a dictionary that may contain precomputed
     successors sets. It is meant to reuse the computation of a previous call to
     `successorssets` when multiple calls are made at the same time. The cache
     dictionary is updated in place. The caller is responsible for its live
     spawn. Code that makes multiple calls to `successorssets` *must* use this
     cache mechanism or suffer terrible performances.
 
     """
 
     succmarkers = repo.obsstore.successors
 
     # Stack of nodes we search successors sets for
     toproceed = [initialnode]
     # set version of above list for fast loop detection
     # element added to "toproceed" must be added here
     stackedset = set(toproceed)
     if cache is None:
         cache = {}
 
     # This while loop is the flattened version of a recursive search for
     # successors sets
     #
     # def successorssets(x):
     #    successors = directsuccessors(x)
     #    ss = [[]]
     #    for succ in directsuccessors(x):
     #        # product as in itertools cartesian product
     #        ss = product(ss, successorssets(succ))
     #    return ss
     #
     # But we can not use plain recursive calls here:
     # - that would blow the python call stack
     # - obsolescence markers may have cycles, we need to handle them.
     #
     # The `toproceed` list act as our call stack. Every node we search
     # successors set for are stacked there.
     #
     # The `stackedset` is set version of this stack used to check if a node is
     # already stacked. This check is used to detect cycles and prevent infinite
     # loop.
     #
     # successors set of all nodes are stored in the `cache` dictionary.
     #
     # After this while loop ends we use the cache to return the successors sets
     # for the node requested by the caller.
     while toproceed:
         # Every iteration tries to compute the successors sets of the topmost
         # node of the stack: CURRENT.
         #
         # There are four possible outcomes:
         #
         # 1) We already know the successors sets of CURRENT:
         #    -> mission accomplished, pop it from the stack.
         # 2) Node is not obsolete:
         #    -> the node is its own successors sets. Add it to the cache.
         # 3) We do not know successors set of direct successors of CURRENT:
         #    -> We add those successors to the stack.
         # 4) We know successors sets of all direct successors of CURRENT:
         #    -> We can compute CURRENT successors set and add it to the
         #       cache.
         #
         current = toproceed[-1]
         if current in cache:
             # case (1): We already know the successors sets
             stackedset.remove(toproceed.pop())
         elif current not in succmarkers:
             # case (2): The node is not obsolete.
             if current in repo:
                 # We have a valid last successors.
                 cache[current] = [(current,)]
             else:
                 # Final obsolete version is unknown locally.
                 # Do not count that as a valid successors
                 cache[current] = []
         else:
             # cases (3) and (4)
             #
             # We proceed in two phases. Phase 1 aims to distinguish case (3)
             # from case (4):
             #
             #     For each direct successors of CURRENT, we check whether its
             #     successors sets are known. If they are not, we stack the
             #     unknown node and proceed to the next iteration of the while
             #     loop. (case 3)
             #
             #     During this step, we may detect obsolescence cycles: a node
             #     with unknown successors sets but already in the call stack.
             #     In such a situation, we arbitrary set the successors sets of
             #     the node to nothing (node pruned) to break the cycle.
             #
             #     If no break was encountered we proceed to phase 2.
             #
             # Phase 2 computes successors sets of CURRENT (case 4); see details
             # in phase 2 itself.
             #
             # Note the two levels of iteration in each phase.
             # - The first one handles obsolescence markers using CURRENT as
             #   precursor (successors markers of CURRENT).
             #
             #   Having multiple entry here means divergence.
             #
             # - The second one handles successors defined in each marker.
             #
             #   Having none means pruned node, multiple successors means split,
             #   single successors are standard replacement.
             #
             for mark in sorted(succmarkers[current]):
                 for suc in mark[1]:
                     if suc not in cache:
                         if suc in stackedset:
                             # cycle breaking
                             cache[suc] = []
                         else:
                             # case (3) If we have not computed successors sets
                             # of one of those successors we add it to the
                             # `toproceed` stack and stop all work for this
                             # iteration.
                             toproceed.append(suc)
                             stackedset.add(suc)
                             break
                 else:
                     continue
                 break
             else:
                 # case (4): we know all successors sets of all direct
                 # successors
                 #
                 # Successors set contributed by each marker depends on the
                 # successors sets of all its "successors" node.
                 #
                 # Each different marker is a divergence in the obsolescence
                 # history. It contributes successors sets distinct from other
                 # markers.
                 #
                 # Within a marker, a successor may have divergent successors
                 # sets. In such a case, the marker will contribute multiple
                 # divergent successors sets. If multiple successors have
                 # divergent successors sets, a cartesian product is used.
                 #
                 # At the end we post-process successors sets to remove
                 # duplicated entry and successors set that are strict subset of
                 # another one.
                 succssets = []
                 for mark in sorted(succmarkers[current]):
                     # successors sets contributed by this marker
                     markss = [[]]
                     for suc in mark[1]:
                         # cardinal product with previous successors
                         productresult = []
                         for prefix in markss:
                             for suffix in cache[suc]:
                                 newss = list(prefix)
                                 for part in suffix:
                                     # do not duplicated entry in successors set
                                     # first entry wins.
                                     if part not in newss:
                                         newss.append(part)
                                 productresult.append(newss)
                         markss = productresult
                     succssets.extend(markss)
                 # remove duplicated and subset
                 seen = []
                 final = []
                 candidate = sorted(((set(s), s) for s in succssets if s),
                                    key=lambda x: len(x[1]), reverse=True)
                 for setversion, listversion in candidate:
                     for seenset in seen:
                         if setversion.issubset(seenset):
                             break
                     else:
                         final.append(listversion)
                         seen.append(setversion)
                 final.reverse() # put small successors set first
                 cache[current] = final
     return cache[initialnode]
 
 def _knownrevs(repo, nodes):
     """yield revision numbers of known nodes passed in parameters
 
     Unknown revisions are silently ignored."""
     torev = repo.changelog.nodemap.get
     for n in nodes:
         rev = torev(n)
         if rev is not None:
             yield rev
 
 # mapping of 'set-name' -> <function to compute this set>
 cachefuncs = {}
 def cachefor(name):
     """Decorator to register a function as computing the cache for a set"""
     def decorator(func):
         assert name not in cachefuncs
         cachefuncs[name] = func
         return func
     return decorator
 
 def getrevs(repo, name):
     """Return the set of revision that belong to the <name> set
 
     Such access may compute the set and cache it for future use"""
     repo = repo.unfiltered()
     if not repo.obsstore:
         return ()
     if name not in repo.obsstore.caches:
         repo.obsstore.caches[name] = cachefuncs[name](repo)
     return repo.obsstore.caches[name]
 
 # To be simple we need to invalidate obsolescence cache when:
 #
 # - new changeset is added:
 # - public phase is changed
 # - obsolescence marker are added
 # - strip is used a repo
 def clearobscaches(repo):
     """Remove all obsolescence related cache from a repo
 
     This remove all cache in obsstore is the obsstore already exist on the
     repo.
 
     (We could be smarter here given the exact event that trigger the cache
     clearing)"""
     # only clear cache is there is obsstore data in this repo
     if 'obsstore' in repo._filecache:
         repo.obsstore.caches.clear()
 
 @cachefor('obsolete')
 def _computeobsoleteset(repo):
     """the set of obsolete revisions"""
     obs = set()
     getrev = repo.changelog.nodemap.get
     getphase = repo._phasecache.phase
     for node in repo.obsstore.successors:
         rev = getrev(node)
         if rev is not None and getphase(repo, rev):
             obs.add(rev)
     return obs
 
 @cachefor('unstable')
 def _computeunstableset(repo):
     """the set of non obsolete revisions with obsolete parents"""
     # revset is not efficient enough here
     # we do (obsolete()::) - obsolete() by hand
     obs = getrevs(repo, 'obsolete')
     if not obs:
         return set()
     cl = repo.changelog
     return set(r for r in cl.descendants(obs) if r not in obs)
 
 @cachefor('suspended')
 def _computesuspendedset(repo):
     """the set of obsolete parents with non obsolete descendants"""
     suspended = repo.changelog.ancestors(getrevs(repo, 'unstable'))
     return set(r for r in getrevs(repo, 'obsolete') if r in suspended)
 
 @cachefor('extinct')
 def _computeextinctset(repo):
     """the set of obsolete parents without non obsolete descendants"""
     return getrevs(repo, 'obsolete') - getrevs(repo, 'suspended')
 
 
 @cachefor('bumped')
 def _computebumpedset(repo):
     """the set of revs trying to obsolete public revisions"""
     bumped = set()
     # utils function (avoid attribut lookup in the loop)
     phase = repo._phasecache.phase # would be faster to grab the full list
     public = phases.public
     cl = repo.changelog
     torev = cl.nodemap.get
     obs = getrevs(repo, 'obsolete')
     for rev in repo:
         # We only evaluate mutable, non-obsolete revision
         if (public < phase(repo, rev)) and (rev not in obs):
             node = cl.node(rev)
             # (future) A cache of precursors may worth if split is very common
             for pnode in allprecursors(repo.obsstore, [node],
                                        ignoreflags=bumpedfix):
                 prev = torev(pnode) # unfiltered! but so is phasecache
                 if (prev is not None) and (phase(repo, prev) <= public):
                     # we have a public precursors
                     bumped.add(rev)
                     break # Next draft!
     return bumped
 
 @cachefor('divergent')
 def _computedivergentset(repo):
     """the set of rev that compete to be the final successors of some revision.
     """
     divergent = set()
     obsstore = repo.obsstore
     newermap = {}
     for ctx in repo.set('(not public()) - obsolete()'):
         mark = obsstore.precursors.get(ctx.node(), ())
         toprocess = set(mark)
         while toprocess:
             prec = toprocess.pop()[0]
             if prec not in newermap:
                 successorssets(repo, prec, newermap)
             newer = [n for n in newermap[prec] if n]
             if len(newer) > 1:
                 divergent.add(ctx.rev())
                 break
             toprocess.update(obsstore.precursors.get(prec, ()))
     return divergent
 
 
 def createmarkers(repo, relations, flag=0, metadata=None):
     """Add obsolete markers between changesets in a repo
 
     <relations> must be an iterable of (<old>, (<new>, ...)) tuple.
     `old` and `news` are changectx.
 
     Trying to obsolete a public changeset will raise an exception.
 
     Current user and date are used except if specified otherwise in the
     metadata attribute.
 
     This function operates within a transaction of its own, but does
     not take any lock on the repo.
     """
     # prepare metadata
     if metadata is None:
         metadata = {}
     if 'date' not in metadata:
         metadata['date'] = '%i %i' % util.makedate()
     if 'user' not in metadata:
         metadata['user'] = repo.ui.username()
     tr = repo.transaction('add-obsolescence-marker')
     try:
         for prec, sucs in relations:
             if not prec.mutable():
                 raise util.Abort("cannot obsolete immutable changeset: %s"
                                  % prec)
             nprec = prec.node()
             nsucs = tuple(s.node() for s in sucs)
             if nprec in nsucs:
                 raise util.Abort("changeset %s cannot obsolete itself" % prec)
             repo.obsstore.create(tr, nprec, nsucs, flag, metadata)
             repo.filteredrevcache.clear()
         tr.close()
     finally:
         tr.release()