annotate hgext/obsolete.py @ 337:ebfd1b96a013 stable

obsolete: convert try to guess what invalid node id are

invalid input are probably short version of node

# obsolete.py - introduce the obsolete concept in mercurial.
#
# Copyright 2011 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.
"""Introduce the Obsolete concept to mercurial

General concept
===============

This extension introduces the *obsolete* concept. It adds a new *obsolete*
relation between two changesets. A relation ``<changeset B> obsolete <changeset
A>`` is set to denote that ``<changeset B>`` is new version of ``<changeset
A>``.

The *obsolete* relation act as a **perpendicular history** to the standard
changeset history. Standard changeset history versions files. The *obsolete*
relation versions changesets.

:obsolete:     a changeset that has been replaced by another one.
:unstable:     a changeset that is not obsolete but has an obsolete ancestor.
:suspended:    an obsolete changeset with unstable descendant.
:extinct:      an obsolete changeset without unstable descendant.
               (subject to garbage collection)

Another name for unstable could be out of sync.


Usage and Feature
=================

Display and Exchange
--------------------

obsolete changesets are hidden. (except if they have non obsolete changeset)

obsolete changesets are not exchanged. This will probably change later but it
was the simpler solution for now.

New commands
------------

Note that rebased changesets are not marked obsolete rather than being stripped
In this experimental extensions, this is done forcing the --keep option. Trying
to use the --keep option of rebase with this extensionn this experimental
extension will cause such a call to abort. Until better releasen please use
graft command to rebase and copy changesets.

Context object
--------------

Context gains a ``obsolete`` method that will return True if a changeset is
obsolete False otherwise.

revset
------

Add an ``obsolete()`` entry.

repo extension
--------------

To Do
~~~~~

- refuse to obsolete published changesets

- handle split

- handle conflict

- handle unstable // out of sync

"""

import os
try:
    from cStringIO import StringIO
except ImportError:
    from StringIO import StringIO

from mercurial.i18n import _

import base64
import json

import struct
from mercurial import util, base85

_pack = struct.pack
_unpack = struct.unpack

from mercurial import util
from mercurial import context
from mercurial import revset
from mercurial import scmutil
from mercurial import extensions
from mercurial import pushkey
from mercurial import discovery
from mercurial import error
from mercurial import commands
from mercurial import changelog
from mercurial import phases
from mercurial.node import hex, bin, short, nullid
from mercurial.lock import release
from mercurial import localrepo
from mercurial import cmdutil
from mercurial import templatekw

try:
    from mercurial.localrepo import storecache
    storecache('babar') # to trigger import
except (TypeError, ImportError):
    def storecache(*args):
        return scmutil.filecache(*args, instore=True)


### Patch changectx
#############################

def obsolete(ctx):
    """is the changeset obsolete by other"""
    if ctx.node()is None:
        return False
    return bool(ctx._repo.obsoletedby(ctx.node())) and ctx.phase()

context.changectx.obsolete = obsolete

def unstable(ctx):
    """is the changeset unstable (have obsolete ancestor)"""
    if ctx.node() is None:
        return False
    return ctx.rev() in ctx._repo._unstableset

context.changectx.unstable = unstable

def extinct(ctx):
    """is the changeset extinct by other"""
    if ctx.node() is None:
        return False
    return ctx.rev() in ctx._repo._extinctset

context.changectx.extinct = extinct

def latecomer(ctx):
    """is the changeset latecomer (Try to succeed to public change)"""
    if ctx.node() is None:
        return False
    return ctx.rev() in ctx._repo._latecomerset

context.changectx.latecomer = latecomer


### revset
#############################

def revsethidden(repo, subset, x):
    """hidden changesets"""
    args = revset.getargs(x, 0, 0, 'hidden takes no argument')
    return [r for r in subset if r in repo.changelog.hiddenrevs]

def revsetobsolete(repo, subset, x):
    """obsolete changesets"""
    args = revset.getargs(x, 0, 0, 'obsolete takes no argument')
    return [r for r in subset if r in repo._obsoleteset and repo._phasecache.phase(repo, r) > 0]

# XXX Backward compatibility, to be removed once stabilized
if '_phasecache' not in vars(localrepo.localrepository): # new api
    def revsetobsolete(repo, subset, x):
        """obsolete changesets"""
        args = revset.getargs(x, 0, 0, 'obsolete takes no argument')
        return [r for r in subset if r in repo._obsoleteset and repo._phaserev[r] > 0]

def revsetunstable(repo, subset, x):
    """non obsolete changesets descendant of obsolete one"""
    args = revset.getargs(x, 0, 0, 'unstable takes no arguments')
    return [r for r in subset if r in repo._unstableset]

def revsetsuspended(repo, subset, x):
    """obsolete changesets with non obsolete descendants"""
    args = revset.getargs(x, 0, 0, 'suspended takes no arguments')
    return [r for r in subset if r in repo._suspendedset]

def revsetextinct(repo, subset, x):
    """obsolete changesets without obsolete descendants"""
    args = revset.getargs(x, 0, 0, 'extinct takes no arguments')
    return [r for r in subset if r in repo._extinctset]

def revsetlatecomer(repo, subset, x):
    """latecomer, Try to succeed to public change"""
    args = revset.getargs(x, 0, 0, 'latecomer takes no arguments')
    return [r for r in subset if r in repo._latecomerset]

def _precursors(repo, s):
    """Precursor of a changeset"""
    cs = set()
    nm = repo.changelog.nodemap
    markerbysubj = repo.obsstore.successors
    for r in s:
        for p in markerbysubj.get(repo[r].node(), ()):
            pr = nm.get(p[0])
            if pr is not None:
                cs.add(pr)
    return cs

def revsetprecursors(repo, subset, x):
    """precursors of a subset"""
    s = revset.getset(repo, range(len(repo)), x)
    cs = _precursors(repo, s)
    return [r for r in subset if r in cs]

def _allprecursors(repo, s):  # XXX we need a better naming
    """transitive precursors of a subset"""
    toproceed = [repo[r].node() for r in s]
    seen = set()
    allsubjects = repo.obsstore.successors
    while toproceed:
        nc = toproceed.pop()
        for mark in allsubjects.get(nc, ()):
            np = mark[0]
            if np not in seen:
                seen.add(np)
                toproceed.append(np)
    nm = repo.changelog.nodemap
    cs = set()
    for p in seen:
        pr = nm.get(p)
        if pr is not None:
            cs.add(pr)
    return cs

def revsetallprecursors(repo, subset, x):
    """obsolete parents"""
    s = revset.getset(repo, range(len(repo)), x)
    cs = _allprecursors(repo, s)
    return [r for r in subset if r in cs]

def _successors(repo, s):
    """Successors of a changeset"""
    cs = set()
    nm = repo.changelog.nodemap
    markerbyobj = repo.obsstore.precursors
    for r in s:
        for p in markerbyobj.get(repo[r].node(), ()):
            for sub in p[1]:
                sr = nm.get(sub)
                if sr is not None:
                    cs.add(sr)
    return cs

def revsetsuccessors(repo, subset, x):
    """successors of a subset"""
    s = revset.getset(repo, range(len(repo)), x)
    cs = _successors(repo, s)
    return [r for r in subset if r in cs]

def _allsuccessors(repo, s):  # XXX we need a better naming
    """transitive successors of a subset"""
    toproceed = [repo[r].node() for r in s]
    seen = set()
    allobjects = repo.obsstore.precursors
    while toproceed:
        nc = toproceed.pop()
        for mark in allobjects.get(nc, ()):
            for sub in mark[1]:
                if sub not in seen:
                    seen.add(sub)
                    toproceed.append(sub)
    nm = repo.changelog.nodemap
    cs = set()
    for s in seen:
        sr = nm.get(s)
        if sr is not None:
            cs.add(sr)
    return cs

def revsetallsuccessors(repo, subset, x):
    """obsolete parents"""
    s = revset.getset(repo, range(len(repo)), x)
    cs = _allsuccessors(repo, s)
    return [r for r in subset if r in cs]


### template keywords
#####################

def obsoletekw(repo, ctx, templ, **args):
    """:obsolete: String. The obsolescence level of the node, could be
    ``stable``, ``unstable``, ``suspended`` or ``extinct``.
    """
    rev = ctx.rev()
    if rev in repo._extinctset:
        return 'extinct'
    if rev in repo._suspendedset:
        return 'suspended'
    if rev in repo._unstableset:
        return 'unstable'
    return 'stable'

### Other Extension compat
############################


def buildstate(orig, repo, dest, rebaseset, *ags, **kws):
    """wrapper for rebase 's buildstate that exclude obsolete changeset"""
    rebaseset = repo.revs('%ld - extinct()', rebaseset)
    return orig(repo, dest, rebaseset, *ags, **kws)

def defineparents(orig, repo, rev, target, state, *args, **kwargs):
    rebasestate = getattr(repo, '_rebasestate', None)
    if rebasestate is not None:
        repo._rebasestate = dict(state)
        repo._rebasetarget = target
    return orig(repo, rev, target, state, *args, **kwargs)

def concludenode(orig, repo, rev, p1, *args, **kwargs):
    """wrapper for rebase 's concludenode that set obsolete relation"""
    newrev = orig(repo, rev, p1, *args, **kwargs)
    rebasestate = getattr(repo, '_rebasestate', None)
    if rebasestate is not None:
        if newrev is not None:
            nrev = repo[newrev].rev()
        else:
            nrev = p1
        repo._rebasestate[rev] = nrev
    return newrev

def cmdrebase(orig, ui, repo, *args, **kwargs):

    reallykeep = kwargs.get('keep', False)
    kwargs = dict(kwargs)
    kwargs['keep'] = True

    # We want to mark rebased revision as obsolete and set their
    # replacements if any. Doing it in concludenode() prevents
    # aborting the rebase, and is not called with all relevant
    # revisions in --collapse case. Instead, we try to track the
    # rebase state structure by sampling/updating it in
    # defineparents() and concludenode(). The obsolete markers are
    # added from this state after a successful call.
    repo._rebasestate = {}
    repo._rebasetarget = None
    try:
        res = orig(ui, repo, *args, **kwargs)
        if not reallykeep:
            # Filter nullmerge or unrebased entries
            repo._rebasestate = dict(p for p in repo._rebasestate.iteritems()
                                     if p[1] >= 0)
            if not res and not kwargs.get('abort') and repo._rebasestate:
                # Rebased revisions are assumed to be descendants of
                # targetrev. If a source revision is mapped to targetrev
                # or to another rebased revision, it must have been
                # removed.
                targetrev = repo[repo._rebasetarget].rev()
                newrevs = set([targetrev])
                replacements = {}
                for rev, newrev in sorted(repo._rebasestate.items()):
                    oldnode = repo[rev].node()
                    if newrev not in newrevs:
                        newnode = repo[newrev].node()
                        newrevs.add(newrev)
                    else:
                        newnode = nullid
                    replacements[oldnode] = newnode

                if kwargs.get('collapse'):
                    newnodes = set(n for n in replacements.values() if n != nullid)
                    if newnodes:
                        # Collapsing into more than one revision?
                        assert len(newnodes) == 1, newnodes
                        newnode = newnodes.pop()
                    else:
                        newnode = nullid
                    repo.addcollapsedobsolete(replacements, newnode)
                else:
                    for oldnode, newnode in replacements.iteritems():
                        repo.addobsolete(newnode, oldnode)
        return res
    finally:
        delattr(repo, '_rebasestate')
        delattr(repo, '_rebasetarget')


def extsetup(ui):

    revset.symbols["hidden"] = revsethidden
    revset.symbols["obsolete"] = revsetobsolete
    revset.symbols["unstable"] = revsetunstable
    revset.symbols["suspended"] = revsetsuspended
    revset.symbols["extinct"] = revsetextinct
    revset.symbols["latecomer"] = revsetlatecomer
    revset.symbols["obsparents"] = revsetprecursors  # DEPR
    revset.symbols["precursors"] = revsetprecursors
    revset.symbols["obsancestors"] = revsetallprecursors  # DEPR
    revset.symbols["allprecursors"] = revsetallprecursors  # bad name
    revset.symbols["successors"] = revsetsuccessors
    revset.symbols["allsuccessors"] = revsetallsuccessors  # bad name

    templatekw.keywords['obsolete'] = obsoletekw

    try:
        rebase = extensions.find('rebase')
        if rebase:
            extensions.wrapfunction(rebase, 'buildstate', buildstate)
            extensions.wrapfunction(rebase, 'defineparents', defineparents)
            extensions.wrapfunction(rebase, 'concludenode', concludenode)
            extensions.wrapcommand(rebase.cmdtable, "rebase", cmdrebase)
    except KeyError:
        pass  # rebase not found

# Pushkey mechanism for mutable
#########################################

def listmarkers(repo):
    """List markers over pushkey"""
    if not repo.obsstore:
        return {}
    data = repo.obsstore._writemarkers()
    return {'dump': base85.b85encode(data)}

def pushmarker(repo, key, old, new):
    """Push markers over pushkey"""
    if key != '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:
        repo.obsstore.mergemarkers(data)
        return 1
    finally:
        lock.release()

pushkey.register('obsolete', pushmarker, listmarkers)

### Discovery wrapping
#############################

class blist(list, object):
    """silly class to have non False but empty list"""

    def __nonzero__(self):
        return bool(len(self.orig))

def wrapfindcommonoutgoing(orig, repo, *args, **kwargs):
    """wrap mercurial.discovery.findcommonoutgoing to remove extinct changeset

    Such excluded changeset are removed from excluded  and will *not* appear
    are excluded secret changeset.
    """
    outgoing = orig(repo, *args, **kwargs)
    orig = outgoing.excluded
    outgoing.excluded = blist(n for n in orig if not repo[n].extinct())
    # when no revision is specified (push everything) a shortcut is taken when
    # nothign was exclude. taking this code path when extinct changeset have
    # been excluded leads to repository corruption.
    outgoing.excluded.orig = orig
    return outgoing

def wrapcheckheads(orig, repo, remote, outgoing, *args, **kwargs):
    """wrap mercurial.discovery.checkheads

    * prevent unstability to be pushed
    * patch remote to ignore obsolete heads on remote
    """
    # do not push instability
    for h in outgoing.missingheads:
        # checking heads only is enought because any thing base on obsolete
        # changeset is either obsolete or unstable.
        ctx =  repo[h]
        hint = _("use 'hg stabilize' to get a stable history (or --force to proceed)")
        if ctx.unstable():
            raise util.Abort(_("Trying to push unstable changeset: %s!") % ctx,
                             hint=hint)
        if ctx.obsolete():
            raise util.Abort(_("Trying to push obsolete changeset: %s!") % ctx,
                             hint=hint)
        if ctx.latecomer():
            raise util.Abort(_("Trying to push latecomer changeset: %s!") % ctx,
                             hint=hint)
    ### patch remote branch map
    # do not read it this burn eyes
    try:
        if 'oldbranchmap' not in vars(remote):
            remote.oldbranchmap = remote.branchmap
            def branchmap():
                newbm = {}
                oldbm = None
                if (util.safehasattr(phases, 'visiblebranchmap')
                    and not util.safehasattr(remote, 'ignorevisiblebranchmap')
                   ):
                    remote.ignorevisiblebranchmap = False
                    remote.branchmap = remote.oldbranchmap
                    oldbm = phases.visiblebranchmap(remote)
                    remote.branchmap = remote.newbranchmap
                    remote.ignorevisiblebranchmap = True
                if oldbm is None:
                    oldbm = remote.oldbranchmap()
                for branch, nodes in oldbm.iteritems():
                    nodes = list(nodes)
                    new = set()
                    while nodes:
                        n = nodes.pop()
                        if n in repo.obsstore.precursors:
                            markers = repo.obsstore.precursors[n]
                            for mark in markers:
                                for newernode in mark[1]:
                                    if newernode is not None:
                                        nodes.append(newernode)
                        else:
                            new.add(n)
                    if new:
                        newbm[branch] = list(new)
                return newbm
            remote.ignorevisiblebranchmap = True
            remote.branchmap = branchmap
            remote.newbranchmap = branchmap
        return orig(repo, remote, outgoing, *args, **kwargs)
    finally:
        remote.__dict__.pop('branchmap', None) # restore class one
        remote.__dict__.pop('oldbranchmap', None)
        remote.__dict__.pop('newbranchmap', None)
        remote.__dict__.pop('ignorevisiblebranchmap', None)

# eye are still burning
def wrapvisiblebranchmap(orig, repo):
    ignore = getattr(repo, 'ignorevisiblebranchmap', None)
    if ignore is None:
        return orig(repo)
    elif ignore:
        return repo.branchmap()
    else:
        return None # break recursion

def wrapclearcache(orig, repo, *args, **kwargs):
    try:
        return orig(repo, *args, **kwargs)
    finally:
        repo._clearobsoletecache()


### New commands
#############################

cmdtable = {}
command = cmdutil.command(cmdtable)

@command('debugobsolete', [], _('SUBJECT OBJECT'))
def cmddebugobsolete(ui, repo, subject, object):
    """add an obsolete relation between two nodes

    The subject is expected to be a newer version of the object.
    """
    lock = repo.lock()
    try:
        sub = repo[subject]
        obj = repo[object]
        repo.addobsolete(sub.node(), obj.node())
    finally:
        lock.release()
    return 0

@command('debugconvertobsolete', [], '')
def cmddebugconvertobsolete(ui, repo):
    """import markers from an .hg/obsolete-relations file"""
    cnt = 0
    err = 0
    l = repo.lock()
    some = False
    try:
        repo._importoldobsolete = True
        store = repo.obsstore
        ### very first format
        try:
            f = repo.opener('obsolete-relations')
            try:
                some = True
                for line in f:
                    subhex, objhex = line.split()
                    suc = bin(subhex)
                    prec = bin(objhex)
                    sucs = (suc==nullid) and [] or [suc]
                    meta = {
                        'date':  '%i %i' % util.makedate(),
                        'user': ui.username(),
                        }
                    store.create(prec, sucs, 0, meta)
                    cnt += 1
            finally:
                f.close()
            util.unlink(repo.join('obsolete-relations'))
        except IOError:
            pass
        ### second (json) format
        data = repo.sopener.tryread('obsoletemarkers')
        if data:
            some = True
            for oldmark in json.loads(data):
                del oldmark['id']  # dropped for now
                del oldmark['reason']  # unused until then
                oldobject = str(oldmark.pop('object'))
                oldsubjects = [str(s) for s in oldmark.pop('subjects')]
                if len(oldobject) != 40:
                    try:
                        oldobject = repo[oldobject].node()
                    except error.RepoLookupError:
                        pass
                if any(len(s) != 40 for s in oldsubjects):
                    try:
                        oldsubjects = [repo[s].node() for s in oldsubjects]
                    except error.RepoLookupError:
                        pass

                oldmark['date'] = '%i %i' % tuple(oldmark['date'])
                try:
                    store.create(bin(oldobject), [bin(n) for n in oldsubjects],
                                 0, oldmark)
                except ValueError:
                    repo.ui.write_err("invalid marker %s -> %s\n"
                                 % (oldobject, oldsubjects))
                    err += 1
                cnt += 1
            util.unlink(repo.sjoin('obsoletemarkers'))
    finally:
        del repo._importoldobsolete
        l.release()
    if not some:
            ui.warn('nothing to do\n')
    ui.status('%i obsolete marker converted\n' % cnt)
    if err:
        ui.write_err('%i conversion failed. check you graph!\n' % err)

@command('debugsuccessors', [], '')
def cmddebugsuccessors(ui, repo):
    """dump obsolete changesets and their successors

    Each line matches an existing marker, the first identifier is the
    obsolete changeset identifier, followed by it successors.
    """
    lock = repo.lock()
    try:
        allsuccessors = repo.obsstore.precursors
        for old in sorted(allsuccessors):
            successors = [sorted(m[1]) for m in allsuccessors[old]]
            for i, group in enumerate(sorted(successors)):
                ui.write('%s' % short(old))
                for new in group:
                    ui.write(' %s' % short(new))
                ui.write('\n')
    finally:
        lock.release()

### Altering existing command
#############################

def wrapmayobsoletewc(origfn, ui, repo, *args, **opts):
    res = origfn(ui, repo, *args, **opts)
    if repo['.'].obsolete():
        ui.warn(_('Working directory parent is obsolete\n'))
    return res

def noextinctsvisibleheads(orig, repo):
    repo._turn_extinct_secret()
    return orig(repo)

def wrapcmdutilamend(orig, ui, repo, commitfunc, old, *args, **kwargs):
    oldnode = old.node()
    new = orig(ui, repo, commitfunc, old, *args, **kwargs)
    if new != oldnode:
        lock = repo.lock()
        try:
            meta = {
                'subjects':  [new],
                'object': oldnode,
                'date':  util.makedate(),
                'user': ui.username(),
                'reason': 'commit --amend',
                }
            repo.obsstore.create(oldnode, [new], 0, meta)
            repo._clearobsoletecache()
            repo._turn_extinct_secret()
        finally:
            lock.release()
    return new

def uisetup(ui):
    extensions.wrapcommand(commands.table, "update", wrapmayobsoletewc)
    extensions.wrapcommand(commands.table, "pull", wrapmayobsoletewc)
    if util.safehasattr(cmdutil, 'amend'):
        extensions.wrapfunction(cmdutil, 'amend', wrapcmdutilamend)
    extensions.wrapfunction(discovery, 'findcommonoutgoing', wrapfindcommonoutgoing)
    extensions.wrapfunction(discovery, 'checkheads', wrapcheckheads)
    extensions.wrapfunction(phases, 'visibleheads', noextinctsvisibleheads)
    extensions.wrapfunction(phases, 'advanceboundary', wrapclearcache)
    if util.safehasattr(phases, 'visiblebranchmap'):
        extensions.wrapfunction(phases, 'visiblebranchmap', wrapvisiblebranchmap)

### serialisation
#############################

def _obsserialise(obssubrels, flike):
    """serialise an obsolete relation mapping in a plain text one

    this is for subject -> [objects] mapping

    format is::

        <subject-full-hex> <object-full-hex>\n"""
    for sub, objs in obssubrels.iteritems():
        for obj in objs:
            if sub is None:
                sub = nullid
            flike.write('%s %s\n' % (hex(sub), hex(obj)))

def _obsdeserialise(flike):
    """read a file like object serialised with _obsserialise

    this desierialize into a {subject -> objects} mapping"""
    rels = {}
    for line in flike:
        subhex, objhex = line.split()
        subnode = bin(subhex)
        if subnode == nullid:
            subnode = None
        rels.setdefault( subnode, set()).add(bin(objhex))
    return rels

### diagnostique tools
#############################

def unstables(repo):
    """Return all unstable changeset"""
    return scmutil.revrange(repo, ['obsolete():: and (not obsolete())'])

def newerversion(repo, obs):
    """Return the newer version of an obsolete changeset"""
    toproceed = set([(obs,)])
    # XXX known optimization available
    newer = set()
    objectrels = repo.obsstore.precursors
    while toproceed:
        current = toproceed.pop()
        assert len(current) <= 1, 'splitting not handled yet. %r' % current
        if current:
            n, = current
            if n in objectrels:
                markers = objectrels[n]
                for mark in markers:
                    toproceed.add(tuple(mark[1]))
            else:
                newer.add(tuple(current))
        else:
            newer.add(())
    return sorted(newer)

### obsolete relation storage
#############################
def add2set(d, key, mark):
    """add <mark> to a `set` in <d>[<key>]"""
    d.setdefault(key, []).append(mark)

def markerid(marker):
    KEYS = ['subjects', "object", "date", "user", "reason"]
    for key in KEYS:
        assert key in marker
    keys = sorted(marker.keys())
    a = util.sha1()
    for key in keys:
        if key == 'subjects':
            for sub in sorted(marker[key]):
                a.update(sub)
        elif key == 'id':
            pass
        else:
            a.update(str(marker[key]))
    a.update('\0')
    return a.digest()

# mercurial backport

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

# data used for parsing and writing
_fmversion = 0
_fmfixed   = '>BIB20s'
_fmnode = '20s'
_fmfsize = struct.calcsize(_fmfixed)
_fnodesize = struct.calcsize(_fmnode)

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')
                             % (len(metadata), mdsize))
        off += mdsize
        yield (pre, sucs, flags, metadata)

class obsstore(object):
    """Store obsolete markers

    Markers can be accessed with two mappings:
    - precursors: old -> set(new)
    - successors: new -> set(old)
    """

    def __init__(self):
        self._all = []
        # new markers to serialize
        self._new = []
        self.precursors = {}
        self.successors = {}

    def __iter__(self):
        return iter(self._all)

    def __nonzero__(self):
        return bool(self._all)

    def create(self, 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 len(prec) != 20:
            raise ValueError(repr(prec))
        for succ in succs:
            if len(succ) != 20:
                raise ValueError((succs))
        marker = (str(prec), tuple(succs), int(flag), encodemeta(metadata))
        self.add(marker)

    def add(self, marker):
        """Add a new marker to the store

        This marker still needs to be written to disk"""
        self._new.append(marker)
        self._load(marker)

    def loadmarkers(self, data):
        """Load all markers in data, mark them as known."""
        for marker in _readmarkers(data):
            self._load(marker)

    def mergemarkers(self, data):
        other = set(_readmarkers(data))
        local = set(self._all)
        new = other - local
        for marker in new:
            self.add(marker)

    def flushmarkers(self, stream):
        """Write all markers to a stream

        After this operation, "new" markers are considered "known"."""
        self._writemarkers(stream)
        self._new[:] = []

    def _load(self, marker):
        self._all.append(marker)
        pre, sucs = marker[:2]
        self.precursors.setdefault(pre, set()).add(marker)
        for suc in sucs:
            self.successors.setdefault(suc, set()).add(marker)

    def _writemarkers(self, stream=None):
        # Kept separate from flushmarkers(), it will be reused for
        # markers exchange.
        if stream is None:
            final = []
            w = final.append
        else:
            w = stream.write
        w(_pack('>B', _fmversion))
        for marker in self._all:
            pre, sucs, flags, metadata = marker
            nbsuc = len(sucs)
            format = _fmfixed + (_fmnode * nbsuc)
            data = [nbsuc, len(metadata), flags, pre]
            data.extend(sucs)
            w(_pack(format, *data))
            w(metadata)
        if stream is None:
            return ''.join(final)


### repo subclassing
#############################

def reposetup(ui, repo):
    if not repo.local():
        return

    opull = repo.pull
    opush = repo.push
    olock = repo.lock
    o_rollback = repo._rollback
    o_updatebranchcache = repo.updatebranchcache

    # /!\ api change in  Hg 2.2 (97efd26eb9576f39590812ea9) /!\
    if util.safehasattr(repo, '_journalfiles'): # Hg 2.2
        o_journalfiles = repo._journalfiles
    o_writejournal = repo._writejournal


    class obsoletingrepo(repo.__class__):

        ### Public method
        def obsoletedby(self, node):
            """return the set of node that make <node> obsolete (obj)"""
            others = set()
            for marker in self.obsstore.precursors.get(node, []):
                others.update(marker[1])
            return others

        def obsolete(self, node):
            """return the set of node that <node> make obsolete (sub)"""
            return set(marker[0] for marker in self.obsstore.successors.get(node, []))

        @storecache('obsstore')
        def obsstore(self):
            if not getattr(self, '_importoldobsolete', False):
                data = repo.opener.tryread('obsolete-relations')
                if not data:
                    data = repo.sopener.tryread('obsoletemarkers')
                if data:
                    raise util.Abort('old format of obsolete marker detected!\n'
                                     'run `hg debugconvertobsolete` once.')
            store = obsstore()
            data = self.sopener.tryread('obsstore')
            if data:
                store.loadmarkers(data)
            return store

        @util.propertycache
        def _obsoleteset(self):
            """the set of obsolete revision"""
            obs = set()
            nm = self.changelog.nodemap
            for obj in self.obsstore.precursors:
                try: # /!\api change in Hg 2.2 (e8d37b78acfb22ae2c1fb126c2)/!\
                    rev = nm.get(obj)
                except TypeError:  #XXX to remove while breaking Hg 2.1 support
                    rev = nm.get(obj, None)
                if rev is not None:
                    obs.add(rev)
            return obs

        @util.propertycache
        def _unstableset(self):
            """the set of non obsolete revision with obsolete parent"""
            return set(self.revs('(obsolete()::) - obsolete()'))

        @util.propertycache
        def _suspendedset(self):
            """the set of obsolete parent with non obsolete descendant"""
            return set(self.revs('obsolete() and obsolete()::unstable()'))

        @util.propertycache
        def _extinctset(self):
            """the set of obsolete parent without non obsolete descendant"""
            return set(self.revs('obsolete() - obsolete()::unstable()'))

        @util.propertycache
        def _latecomerset(self):
            """the set of rev trying to obsolete public revision"""
            query = 'allsuccessors(public()) - obsolete() - public()'
            return set(self.revs(query))

        def _clearobsoletecache(self):
            if '_obsoleteset' in vars(self):
                del self._obsoleteset
            self._clearunstablecache()

        def updatebranchcache(self):
            o_updatebranchcache()
            self._clearunstablecache()

        def _clearunstablecache(self):
            if '_unstableset' in vars(self):
                del self._unstableset
            if '_suspendedset' in vars(self):
                del self._suspendedset
            if '_extinctset' in vars(self):
                del self._extinctset
            if '_latecomerset' in vars(self):
                del self._latecomerset

        def addobsolete(self, sub, obj):
            """Add a relation marking that node <sub> is a new version of <obj>"""
            assert sub != obj
            if not repo[obj].phase():
                if sub is None:
                    self.ui.warn(
                        _("trying to kill immutable changeset %(obj)s\n")
                        % {'obj': short(obj)})
                if sub is not None:
                    self.ui.warn(
                        _("%(sub)s try to obsolete immutable changeset %(obj)s\n")
                        % {'sub': short(sub), 'obj': short(obj)})
            lock = self.lock()
            try:
                meta = {
                    'date':  util.makedate(),
                    'user': ui.username(),
                    'reason': 'unknown',
                    }
                subs = (sub == nullid) and [] or [sub]
                mid = self.obsstore.create(obj, subs, 0, meta)
                self._clearobsoletecache()
                self._turn_extinct_secret()
                return mid
            finally:
                lock.release()

        def addcollapsedobsolete(self, oldnodes, newnode):
            """Mark oldnodes as collapsed into newnode."""
            # Assume oldnodes are all descendants of a single rev
            rootrevs = self.revs('roots(%ln)', oldnodes)
            assert len(rootrevs) == 1, rootrevs
            rootnode = self[rootrevs[0]].node()
            for n in oldnodes:
                self.addobsolete(newnode, n)

        def _turn_extinct_secret(self):
            """ensure all extinct changeset are secret"""
            self._clearobsoletecache()
            # this is mainly for safety purpose
            # both pull and push
            query = '(obsolete() - obsolete()::(unstable() - secret())) - secret()'
            expobs = [c.node() for c in repo.set(query)]
            phases.retractboundary(repo, 2, expobs)

        ### Disk IO

        def lock(self, *args, **kwargs):
            l = olock(*args, **kwargs)
            if not getattr(l.releasefn, 'obspatched', False):
                oreleasefn = l.releasefn
                def releasefn(*args, **kwargs):
                    if 'obsstore' in vars(self) and self.obsstore._new:
                        f = self.sopener('obsstore', 'wb', atomictemp=True)
                        try:
                            self.obsstore.flushmarkers(f)
                            f.close()
                        except: # re-raises
                            f.discard()
                            raise
                    oreleasefn(*args, **kwargs)
                releasefn.obspatched = True
                l.releasefn = releasefn
            return l


        ### pull // push support

        def pull(self, remote, *args, **kwargs):
            """wrapper around push that push obsolete relation"""
            l = repo.lock()
            try:
                result = opull(remote, *args, **kwargs)
                remoteobs = remote.listkeys('obsolete')
                if 'dump' in remoteobs:
                    data = base85.b85decode(remoteobs['dump'])
                    self.obsstore.mergemarkers(data)
                    self._clearobsoletecache()
                    self._turn_extinct_secret()
                    return result
            finally:
                l.release()

        def push(self, remote, *args, **opts):
            """wrapper around pull that pull obsolete relation"""
            self._turn_extinct_secret()
            result = opush(remote, *args, **opts)
            if 'obsolete' in self.listkeys('namespaces') and self.obsstore:
                data = self.obsstore._writemarkers()
                r = remote.pushkey('obsolete', 'dump', '',
                                   base85.b85encode(data))
                if not r:
                    self.ui.warn(_('failed to push obsolete markers!\n'))
            self._turn_extinct_secret()

            return result


        ### rollback support

        # /!\ api change in  Hg 2.2 (97efd26eb9576f39590812ea9) /!\
        if util.safehasattr(repo, '_journalfiles'): # Hg 2.2
            def _journalfiles(self):
                return o_journalfiles() + (self.sjoin('journal.obsstore'),) 

            def _writejournal(self, desc):
                """wrapped version of _writejournal that save obsolete data"""
                o_writejournal(desc)
                filename = 'obsstore'
                filepath = self.sjoin(filename)
                if os.path.exists(filepath):
                    journalname = 'journal.' + filename
                    journalpath = self.sjoin(journalname)
                    util.copyfile(filepath, journalpath)

        else: # XXX removing this bloc will break Hg 2.1 support
            def _writejournal(self, desc):
                """wrapped version of _writejournal that save obsolete data"""
                entries = list(o_writejournal(desc))
                filename = 'obsstore'
                filepath = self.sjoin(filename)
                if  os.path.exists(filepath):
                    journalname = 'journal.' + filename
                    journalpath = self.sjoin(journalname)
                    util.copyfile(filepath, journalpath)
                    entries.append(journalpath)
                return tuple(entries)

        def _rollback(self, dryrun, force):
            """wrapped version of _rollback that restore obsolete data"""
            ret = o_rollback(dryrun, force)
            if not (ret or dryrun): #rollback did not failed
                src = self.sjoin('undo.obsstore')
                dst = self.sjoin('obsstore')
                if os.path.exists(src):
                    util.rename(src, dst)
                elif os.path.exists(dst):
                    # If no state was saved because the file did not existed before.
                    os.unlink(dst)
                # invalidate cache
                self.__dict__.pop('obsstore', None)
            return ret

        @storecache('00changelog.i')
        def changelog(self):
            # << copy pasted from mercurial source
            c = changelog.changelog(self.sopener)
            if 'HG_PENDING' in os.environ:
                p = os.environ['HG_PENDING']
                if p.startswith(self.root):
                    c.readpending('00changelog.i.a')
            # >> end of the copy paste
            old = c.__dict__.pop('hiddenrevs', ())
            if old:
                ui.warn("old wasn't empty ? %r" % old)
            def _sethidden(c, value):
                assert not value


            class hchangelog(c.__class__):
                @util.propertycache
                def hiddenrevs(c):
                    shown = ['not obsolete()', '.', 'bookmark()', 'tagged()',
                             'public()']
                    basicquery = 'obsolete() - (::(%s))' % (' or '.join(shown))
                    # !!! self is repo not changelog
                    result = set(scmutil.revrange(self, [basicquery]))
                    return result
            c.__class__ = hchangelog
            return c

    repo.__class__ = obsoletingrepo