transaction: use 'location' instead of 'vfs' objects for file generation

The argument is now a location name. The location must be present in the
'vfsmap' provided to the transaction at creation time.

mercurial/bookmarks.py

@@ -1,442 +1,442
 # Mercurial bookmark support code
 #
 # Copyright 2008 David Soria Parra <[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 mercurial.i18n import _
 from mercurial.node import hex, bin
 from mercurial import encoding, error, util, obsolete, lock as lockmod
 import errno
 
 class bmstore(dict):
     """Storage for bookmarks.
 
     This object should do all bookmark reads and writes, so that it's
     fairly simple to replace the storage underlying bookmarks without
     having to clone the logic surrounding bookmarks.
 
     This particular bmstore implementation stores bookmarks as
     {hash}\s{name}\n (the same format as localtags) in
     .hg/bookmarks. The mapping is stored as {name: nodeid}.
 
     This class does NOT handle the "current" bookmark state at this
     time.
     """
 
     def __init__(self, repo):
         dict.__init__(self)
         self._repo = repo
         try:
             for line in repo.vfs('bookmarks'):
                 line = line.strip()
                 if not line:
                     continue
                 if ' ' not in line:
                     repo.ui.warn(_('malformed line in .hg/bookmarks: %r\n')
                                  % line)
                     continue
                 sha, refspec = line.split(' ', 1)
                 refspec = encoding.tolocal(refspec)
                 try:
                     self[refspec] = repo.changelog.lookup(sha)
                 except LookupError:
                     pass
         except IOError, inst:
             if inst.errno != errno.ENOENT:
                 raise
 
     def recordchange(self, tr):
         """record that bookmarks have been changed in a transaction
 
         The transaction is then responsible for updating the file content."""
         tr.addfilegenerator('bookmarks', ('bookmarks',), self._write,
-                            vfs=self._repo.vfs)
+                            location='plain')
         tr.hookargs['bookmark_moved'] = '1'
 
     def write(self):
         '''Write bookmarks
 
         Write the given bookmark => hash dictionary to the .hg/bookmarks file
         in a format equal to those of localtags.
 
         We also store a backup of the previous state in undo.bookmarks that
         can be copied back on rollback.
         '''
         repo = self._repo
         if repo._bookmarkcurrent not in self:
             unsetcurrent(repo)
 
         wlock = repo.wlock()
         try:
 
             file = repo.vfs('bookmarks', 'w', atomictemp=True)
             self._write(file)
             file.close()
 
             # touch 00changelog.i so hgweb reloads bookmarks (no lock needed)
             try:
                 repo.svfs.utime('00changelog.i', None)
             except OSError:
                 pass
 
         finally:
             wlock.release()
 
     def _write(self, fp):
         for name, node in self.iteritems():
             fp.write("%s %s\n" % (hex(node), encoding.fromlocal(name)))
 
 def readcurrent(repo):
     '''Get the current bookmark
 
     If we use gittish branches we have a current bookmark that
     we are on. This function returns the name of the bookmark. It
     is stored in .hg/bookmarks.current
     '''
     mark = None
     try:
         file = repo.opener('bookmarks.current')
     except IOError, inst:
         if inst.errno != errno.ENOENT:
             raise
         return None
     try:
         # No readline() in osutil.posixfile, reading everything is cheap
         mark = encoding.tolocal((file.readlines() or [''])[0])
         if mark == '' or mark not in repo._bookmarks:
             mark = None
     finally:
         file.close()
     return mark
 
 def setcurrent(repo, mark):
     '''Set the name of the bookmark that we are currently on
 
     Set the name of the bookmark that we are on (hg update <bookmark>).
     The name is recorded in .hg/bookmarks.current
     '''
     if mark not in repo._bookmarks:
         raise AssertionError('bookmark %s does not exist!' % mark)
 
     current = repo._bookmarkcurrent
     if current == mark:
         return
 
     wlock = repo.wlock()
     try:
         file = repo.opener('bookmarks.current', 'w', atomictemp=True)
         file.write(encoding.fromlocal(mark))
         file.close()
     finally:
         wlock.release()
     repo._bookmarkcurrent = mark
 
 def unsetcurrent(repo):
     wlock = repo.wlock()
     try:
         try:
             repo.vfs.unlink('bookmarks.current')
             repo._bookmarkcurrent = None
         except OSError, inst:
             if inst.errno != errno.ENOENT:
                 raise
     finally:
         wlock.release()
 
 def iscurrent(repo, mark=None, parents=None):
     '''Tell whether the current bookmark is also active
 
     I.e., the bookmark listed in .hg/bookmarks.current also points to a
     parent of the working directory.
     '''
     if not mark:
         mark = repo._bookmarkcurrent
     if not parents:
         parents = [p.node() for p in repo[None].parents()]
     marks = repo._bookmarks
     return (mark in marks and marks[mark] in parents)
 
 def updatecurrentbookmark(repo, oldnode, curbranch):
     try:
         return update(repo, oldnode, repo.branchtip(curbranch))
     except error.RepoLookupError:
         if curbranch == "default": # no default branch!
             return update(repo, oldnode, repo.lookup("tip"))
         else:
             raise util.Abort(_("branch %s not found") % curbranch)
 
 def deletedivergent(repo, deletefrom, bm):
     '''Delete divergent versions of bm on nodes in deletefrom.
 
     Return True if at least one bookmark was deleted, False otherwise.'''
     deleted = False
     marks = repo._bookmarks
     divergent = [b for b in marks if b.split('@', 1)[0] == bm.split('@', 1)[0]]
     for mark in divergent:
         if mark == '@' or '@' not in mark:
             # can't be divergent by definition
             continue
         if mark and marks[mark] in deletefrom:
             if mark != bm:
                 del marks[mark]
                 deleted = True
     return deleted
 
 def calculateupdate(ui, repo, checkout):
     '''Return a tuple (targetrev, movemarkfrom) indicating the rev to
     check out and where to move the active bookmark from, if needed.'''
     movemarkfrom = None
     if checkout is None:
         curmark = repo._bookmarkcurrent
         if iscurrent(repo):
             movemarkfrom = repo['.'].node()
         elif curmark:
             ui.status(_("updating to active bookmark %s\n") % curmark)
             checkout = curmark
     return (checkout, movemarkfrom)
 
 def update(repo, parents, node):
     deletefrom = parents
     marks = repo._bookmarks
     update = False
     cur = repo._bookmarkcurrent
     if not cur:
         return False
 
     if marks[cur] in parents:
         new = repo[node]
         divs = [repo[b] for b in marks
                 if b.split('@', 1)[0] == cur.split('@', 1)[0]]
         anc = repo.changelog.ancestors([new.rev()])
         deletefrom = [b.node() for b in divs if b.rev() in anc or b == new]
         if validdest(repo, repo[marks[cur]], new):
             marks[cur] = new.node()
             update = True
 
     if deletedivergent(repo, deletefrom, cur):
         update = True
 
     if update:
         marks.write()
     return update
 
 def listbookmarks(repo):
     # We may try to list bookmarks on a repo type that does not
     # support it (e.g., statichttprepository).
     marks = getattr(repo, '_bookmarks', {})
 
     d = {}
     hasnode = repo.changelog.hasnode
     for k, v in marks.iteritems():
         # don't expose local divergent bookmarks
         if hasnode(v) and ('@' not in k or k.endswith('@')):
             d[k] = hex(v)
     return d
 
 def pushbookmark(repo, key, old, new):
     w = l = tr = None
     try:
         w = repo.wlock()
         l = repo.lock()
         tr = repo.transaction('bookmarks')
         marks = repo._bookmarks
         existing = hex(marks.get(key, ''))
         if existing != old and existing != new:
             return False
         if new == '':
             del marks[key]
         else:
             if new not in repo:
                 return False
             marks[key] = repo[new].node()
         marks.recordchange(tr)
         tr.close()
         return True
     finally:
         lockmod.release(tr, l, w)
 
 def compare(repo, srcmarks, dstmarks,
             srchex=None, dsthex=None, targets=None):
     '''Compare bookmarks between srcmarks and dstmarks
 
     This returns tuple "(addsrc, adddst, advsrc, advdst, diverge,
     differ, invalid)", each are list of bookmarks below:
 
     :addsrc:  added on src side (removed on dst side, perhaps)
     :adddst:  added on dst side (removed on src side, perhaps)
     :advsrc:  advanced on src side
     :advdst:  advanced on dst side
     :diverge: diverge
     :differ:  changed, but changeset referred on src is unknown on dst
     :invalid: unknown on both side
     :same:    same on both side
 
     Each elements of lists in result tuple is tuple "(bookmark name,
     changeset ID on source side, changeset ID on destination
     side)". Each changeset IDs are 40 hexadecimal digit string or
     None.
 
     Changeset IDs of tuples in "addsrc", "adddst", "differ" or
      "invalid" list may be unknown for repo.
 
     This function expects that "srcmarks" and "dstmarks" return
     changeset ID in 40 hexadecimal digit string for specified
     bookmark. If not so (e.g. bmstore "repo._bookmarks" returning
     binary value), "srchex" or "dsthex" should be specified to convert
     into such form.
 
     If "targets" is specified, only bookmarks listed in it are
     examined.
     '''
     if not srchex:
         srchex = lambda x: x
     if not dsthex:
         dsthex = lambda x: x
 
     if targets:
         bset = set(targets)
     else:
         srcmarkset = set(srcmarks)
         dstmarkset = set(dstmarks)
         bset = srcmarkset | dstmarkset
 
     results = ([], [], [], [], [], [], [], [])
     addsrc = results[0].append
     adddst = results[1].append
     advsrc = results[2].append
     advdst = results[3].append
     diverge = results[4].append
     differ = results[5].append
     invalid = results[6].append
     same = results[7].append
 
     for b in sorted(bset):
         if b not in srcmarks:
             if b in dstmarks:
                 adddst((b, None, dsthex(dstmarks[b])))
             else:
                 invalid((b, None, None))
         elif b not in dstmarks:
             addsrc((b, srchex(srcmarks[b]), None))
         else:
             scid = srchex(srcmarks[b])
             dcid = dsthex(dstmarks[b])
             if scid == dcid:
                 same((b, scid, dcid))
             elif scid in repo and dcid in repo:
                 sctx = repo[scid]
                 dctx = repo[dcid]
                 if sctx.rev() < dctx.rev():
                     if validdest(repo, sctx, dctx):
                         advdst((b, scid, dcid))
                     else:
                         diverge((b, scid, dcid))
                 else:
                     if validdest(repo, dctx, sctx):
                         advsrc((b, scid, dcid))
                     else:
                         diverge((b, scid, dcid))
             else:
                 # it is too expensive to examine in detail, in this case
                 differ((b, scid, dcid))
 
     return results
 
 def _diverge(ui, b, path, localmarks):
     if b == '@':
         b = ''
     # find a unique @ suffix
     for x in range(1, 100):
         n = '%s@%d' % (b, x)
         if n not in localmarks:
             break
     # try to use an @pathalias suffix
     # if an @pathalias already exists, we overwrite (update) it
     if path.startswith("file:"):
         path = util.url(path).path
     for p, u in ui.configitems("paths"):
         if u.startswith("file:"):
             u = util.url(u).path
         if path == u:
             n = '%s@%s' % (b, p)
     return n
 
 def updatefromremote(ui, repo, remotemarks, path, trfunc, explicit=()):
     ui.debug("checking for updated bookmarks\n")
     localmarks = repo._bookmarks
     (addsrc, adddst, advsrc, advdst, diverge, differ, invalid, same
      ) = compare(repo, remotemarks, localmarks, dsthex=hex)
 
     status = ui.status
     warn = ui.warn
     if ui.configbool('ui', 'quietbookmarkmove', False):
         status = warn = ui.debug
 
     explicit = set(explicit)
     changed = []
     for b, scid, dcid in addsrc:
         if scid in repo: # add remote bookmarks for changes we already have
             changed.append((b, bin(scid), status,
                             _("adding remote bookmark %s\n") % (b)))
     for b, scid, dcid in advsrc:
         changed.append((b, bin(scid), status,
                         _("updating bookmark %s\n") % (b)))
     # remove normal movement from explicit set
     explicit.difference_update(d[0] for d in changed)
 
     for b, scid, dcid in diverge:
         if b in explicit:
             explicit.discard(b)
             changed.append((b, bin(scid), status,
                             _("importing bookmark %s\n") % (b)))
         else:
             db = _diverge(ui, b, path, localmarks)
             changed.append((db, bin(scid), warn,
                             _("divergent bookmark %s stored as %s\n")
                             % (b, db)))
     for b, scid, dcid in adddst + advdst:
         if b in explicit:
             explicit.discard(b)
             changed.append((b, bin(scid), status,
                             _("importing bookmark %s\n") % (b)))
 
     if changed:
         tr = trfunc()
         for b, node, writer, msg in sorted(changed):
             localmarks[b] = node
             writer(msg)
         localmarks.recordchange(tr)
 
 def diff(ui, dst, src):
     ui.status(_("searching for changed bookmarks\n"))
 
     smarks = src.listkeys('bookmarks')
     dmarks = dst.listkeys('bookmarks')
 
     diff = sorted(set(smarks) - set(dmarks))
     for k in diff:
         mark = ui.debugflag and smarks[k] or smarks[k][:12]
         ui.write("   %-25s %s\n" % (k, mark))
 
     if len(diff) <= 0:
         ui.status(_("no changed bookmarks found\n"))
         return 1
     return 0
 
 def validdest(repo, old, new):
     """Is the new bookmark destination a valid update from the old one"""
     repo = repo.unfiltered()
     if old == new:
         # Old == new -> nothing to update.
         return False
     elif not old:
         # old is nullrev, anything is valid.
         # (new != nullrev has been excluded by the previous check)
         return True
     elif repo.obsstore:
         return new.node() in obsolete.foreground(repo, [old.node()])
     else:
         # still an independent clause as it is lazyer (and therefore faster)
         return old.descendant(new)

mercurial/transaction.py

@@ -1,502 +1,505
 # transaction.py - simple journaling scheme for mercurial
 #
 # This transaction scheme is intended to gracefully handle program
 # errors and interruptions. More serious failures like system crashes
 # can be recovered with an fsck-like tool. As the whole repository is
 # effectively log-structured, this should amount to simply truncating
 # anything that isn't referenced in the changelog.
 #
 # Copyright 2005, 2006 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 _
 import os
 import errno
 import error, util
 
 version = 2
 
 def active(func):
     def _active(self, *args, **kwds):
         if self.count == 0:
             raise error.Abort(_(
                 'cannot use transaction when it is already committed/aborted'))
         return func(self, *args, **kwds)
     return _active
 
 def _playback(journal, report, opener, vfsmap, entries, backupentries,
               unlink=True):
     for f, o, _ignore in entries:
         if o or not unlink:
             try:
                 fp = opener(f, 'a')
                 fp.truncate(o)
                 fp.close()
             except IOError:
                 report(_("failed to truncate %s\n") % f)
                 raise
         else:
             try:
                 opener.unlink(f)
             except (IOError, OSError), inst:
                 if inst.errno != errno.ENOENT:
                     raise
 
     backupfiles = []
     for l, f, b, c in backupentries:
         if l not in vfsmap and c:
             report("couldn't handle %s: unknown cache location %s\n"
                         % (b, l))
         vfs = vfsmap[l]
         try:
             if f and b:
                 filepath = vfs.join(f)
                 backuppath = vfs.join(b)
                 try:
                     util.copyfile(backuppath, filepath)
                     backupfiles.append(b)
                 except IOError:
                     report(_("failed to recover %s\n") % f)
             else:
                 target = f or b
                 try:
                     vfs.unlink(target)
                 except (IOError, OSError), inst:
                     if inst.errno != errno.ENOENT:
                         raise
         except (IOError, OSError, util.Abort), inst:
             if not c:
                 raise
 
     opener.unlink(journal)
     backuppath = "%s.backupfiles" % journal
     if opener.exists(backuppath):
         opener.unlink(backuppath)
     try:
         for f in backupfiles:
             if opener.exists(f):
                 opener.unlink(f)
     except (IOError, OSError, util.Abort), inst:
         # only pure backup file remains, it is sage to ignore any error
         pass
 
 class transaction(object):
     def __init__(self, report, opener, vfsmap, journal, after=None,
                  createmode=None, onclose=None, onabort=None):
         """Begin a new transaction
 
         Begins a new transaction that allows rolling back writes in the event of
         an exception.
 
         * `after`: called after the transaction has been committed
         * `createmode`: the mode of the journal file that will be created
         * `onclose`: called as the transaction is closing, but before it is
         closed
         * `onabort`: called as the transaction is aborting, but before any files
         have been truncated
         """
         self.count = 1
         self.usages = 1
         self.report = report
         # a vfs to the store content
         self.opener = opener
         # a map to access file in various {location -> vfs}
         vfsmap = vfsmap.copy()
         vfsmap[''] = opener  # set default value
         self._vfsmap = vfsmap
         self.after = after
         self.onclose = onclose
         self.onabort = onabort
         self.entries = []
         self.map = {}
         self.journal = journal
         self._queue = []
         # a dict of arguments to be passed to hooks
         self.hookargs = {}
         self.file = opener.open(self.journal, "w")
 
         # a list of ('location', 'path', 'backuppath', cache) entries.
         # - if 'backuppath' is empty, no file existed at backup time
         # - if 'path' is empty, this is a temporary transaction file
         # - if 'location' is not empty, the path is outside main opener reach.
         #   use 'location' value as a key in a vfsmap to find the right 'vfs'
         # (cache is currently unused)
         self._backupentries = []
         self._backupmap = {}
         self._backupjournal = "%s.backupfiles" % journal
         self._backupsfile = opener.open(self._backupjournal, 'w')
         self._backupsfile.write('%d\n' % version)
 
         if createmode is not None:
             opener.chmod(self.journal, createmode & 0666)
             opener.chmod(self._backupjournal, createmode & 0666)
 
         # hold file generations to be performed on commit
         self._filegenerators = {}
         # hold callbalk to write pending data for hooks
         self._pendingcallback = {}
         # True is any pending data have been written ever
         self._anypending = False
         # holds callback to call when writing the transaction
         self._finalizecallback = {}
         # hold callbalk for post transaction close
         self._postclosecallback = {}
 
     def __del__(self):
         if self.journal:
             self._abort()
 
     @active
     def startgroup(self):
         """delay registration of file entry
 
         This is used by strip to delay vision of strip offset. The transaction
         sees either none or all of the strip actions to be done."""
         self._queue.append([])
 
     @active
     def endgroup(self):
         """apply delayed registration of file entry.
 
         This is used by strip to delay vision of strip offset. The transaction
         sees either none or all of the strip actions to be done."""
         q = self._queue.pop()
         for f, o, data in q:
             self._addentry(f, o, data)
 
     @active
     def add(self, file, offset, data=None):
         """record the state of an append-only file before update"""
         if file in self.map or file in self._backupmap:
             return
         if self._queue:
             self._queue[-1].append((file, offset, data))
             return
 
         self._addentry(file, offset, data)
 
     def _addentry(self, file, offset, data):
         """add a append-only entry to memory and on-disk state"""
         if file in self.map or file in self._backupmap:
             return
         self.entries.append((file, offset, data))
         self.map[file] = len(self.entries) - 1
         # add enough data to the journal to do the truncate
         self.file.write("%s\0%d\n" % (file, offset))
         self.file.flush()
 
     @active
     def addbackup(self, file, hardlink=True, location=''):
         """Adds a backup of the file to the transaction
 
         Calling addbackup() creates a hardlink backup of the specified file
         that is used to recover the file in the event of the transaction
         aborting.
 
         * `file`: the file path, relative to .hg/store
         * `hardlink`: use a hardlink to quickly create the backup
         """
         if self._queue:
             msg = 'cannot use transaction.addbackup inside "group"'
             raise RuntimeError(msg)
 
         if file in self.map or file in self._backupmap:
             return
         dirname, filename = os.path.split(file)
         backupfilename = "%s.backup.%s" % (self.journal, filename)
         backupfile = os.path.join(dirname, backupfilename)
         vfs = self._vfsmap[location]
         if vfs.exists(file):
             filepath = vfs.join(file)
             backuppath = vfs.join(backupfile)
             util.copyfiles(filepath, backuppath, hardlink=hardlink)
         else:
             backupfile = ''
 
         self._addbackupentry((location, file, backupfile, False))
 
     def _addbackupentry(self, entry):
         """register a new backup entry and write it to disk"""
         self._backupentries.append(entry)
         self._backupmap[file] = len(self._backupentries) - 1
         self._backupsfile.write("%s\0%s\0%s\0%d\n" % entry)
         self._backupsfile.flush()
 
     @active
     def registertmp(self, tmpfile):
         """register a temporary transaction file
 
         Such file will be delete when the transaction exit (on both failure and
         success).
         """
         self._addbackupentry(('', '', tmpfile, False))
 
     @active
-    def addfilegenerator(self, genid, filenames, genfunc, order=0, vfs=None):
+    def addfilegenerator(self, genid, filenames, genfunc, order=0,
+                         location=''):
         """add a function to generates some files at transaction commit
 
         The `genfunc` argument is a function capable of generating proper
         content of each entry in the `filename` tuple.
 
         At transaction close time, `genfunc` will be called with one file
         object argument per entries in `filenames`.
 
         The transaction itself is responsible for the backup, creation and
         final write of such file.
 
         The `genid` argument is used to ensure the same set of file is only
         generated once. Call to `addfilegenerator` for a `genid` already
         present will overwrite the old entry.
 
         The `order` argument may be used to control the order in which multiple
         generator will be executed.
+
+        The `location` arguments may be used to indicate the files are located
+        outside of the the standard directory for transaction. It should match
+        one of the key of the `transaction.vfsmap` dictionnary.
         """
         # For now, we are unable to do proper backup and restore of custom vfs
         # but for bookmarks that are handled outside this mechanism.
-        assert vfs is None or filenames == ('bookmarks',)
-        self._filegenerators[genid] = (order, filenames, genfunc, vfs)
+        self._filegenerators[genid] = (order, filenames, genfunc, location)
 
     def _generatefiles(self):
         # write files registered for generation
         for entry in sorted(self._filegenerators.values()):
-            order, filenames, genfunc, vfs = entry
-            if vfs is None:
-                vfs = self.opener
+            order, filenames, genfunc, location = entry
+            vfs = self._vfsmap[location]
             files = []
             try:
                 for name in filenames:
                     # Some files are already backed up when creating the
                     # localrepo. Until this is properly fixed we disable the
                     # backup for them.
                     if name not in ('phaseroots', 'bookmarks'):
-                        self.addbackup(name)
+                        self.addbackup(name, location=location)
                     files.append(vfs(name, 'w', atomictemp=True))
                 genfunc(*files)
             finally:
                 for f in files:
                     f.close()
 
     @active
     def find(self, file):
         if file in self.map:
             return self.entries[self.map[file]]
         if file in self._backupmap:
             return self._backupentries[self._backupmap[file]]
         return None
 
     @active
     def replace(self, file, offset, data=None):
         '''
         replace can only replace already committed entries
         that are not pending in the queue
         '''
 
         if file not in self.map:
             raise KeyError(file)
         index = self.map[file]
         self.entries[index] = (file, offset, data)
         self.file.write("%s\0%d\n" % (file, offset))
         self.file.flush()
 
     @active
     def nest(self):
         self.count += 1
         self.usages += 1
         return self
 
     def release(self):
         if self.count > 0:
             self.usages -= 1
         # if the transaction scopes are left without being closed, fail
         if self.count > 0 and self.usages == 0:
             self._abort()
 
     def running(self):
         return self.count > 0
 
     def addpending(self, category, callback):
         """add a callback to be called when the transaction is pending
 
         The transaction will be given as callback's first argument.
 
         Category is a unique identifier to allow overwriting an old callback
         with a newer callback.
         """
         self._pendingcallback[category] = callback
 
     @active
     def writepending(self):
         '''write pending file to temporary version
 
         This is used to allow hooks to view a transaction before commit'''
         categories = sorted(self._pendingcallback)
         for cat in categories:
             # remove callback since the data will have been flushed
             any = self._pendingcallback.pop(cat)(self)
             self._anypending = self._anypending or any
         return self._anypending
 
     @active
     def addfinalize(self, category, callback):
         """add a callback to be called when the transaction is closed
 
         The transaction will be given as callback's first argument.
 
         Category is a unique identifier to allow overwriting old callbacks with
         newer callbacks.
         """
         self._finalizecallback[category] = callback
 
     @active
     def addpostclose(self, category, callback):
         """add a callback to be called after the transaction is closed
 
         The transaction will be given as callback's first argument.
 
         Category is a unique identifier to allow overwriting an old callback
         with a newer callback.
         """
         self._postclosecallback[category] = callback
 
     @active
     def close(self):
         '''commit the transaction'''
         if self.count == 1:
             self._generatefiles()
             categories = sorted(self._finalizecallback)
             for cat in categories:
                 self._finalizecallback[cat](self)
             if self.onclose is not None:
                 self.onclose()
 
         self.count -= 1
         if self.count != 0:
             return
         self.file.close()
         self._backupsfile.close()
         # cleanup temporary files
         for l, f, b, c in self._backupentries:
             if l not in self._vfsmap and c:
                 self.report("couldn't remote %s: unknown cache location %s\n"
                             % (b, l))
                 continue
             vfs = self._vfsmap[l]
             if not f and b and vfs.exists(b):
                 try:
                     vfs.unlink(b)
                 except (IOError, OSError, util.Abort), inst:
                     if not c:
                         raise
                     # Abort may be raise by read only opener
                     self.report("couldn't remote %s: %s\n"
                                 % (vfs.join(b), inst))
         self.entries = []
         if self.after:
             self.after()
         if self.opener.isfile(self.journal):
             self.opener.unlink(self.journal)
         if self.opener.isfile(self._backupjournal):
             self.opener.unlink(self._backupjournal)
             for _l, _f, b, c in self._backupentries:
                 if l not in self._vfsmap and c:
                     self.report("couldn't remote %s: unknown cache location"
                                 "%s\n" % (b, l))
                     continue
                 vfs = self._vfsmap[l]
                 if b and vfs.exists(b):
                     try:
                         vfs.unlink(b)
                     except (IOError, OSError, util.Abort), inst:
                         if not c:
                             raise
                         # Abort may be raise by read only opener
                         self.report("couldn't remote %s: %s\n"
                                     % (vfs.join(b), inst))
         self._backupentries = []
         self.journal = None
         # run post close action
         categories = sorted(self._postclosecallback)
         for cat in categories:
             self._postclosecallback[cat](self)
 
     @active
     def abort(self):
         '''abort the transaction (generally called on error, or when the
         transaction is not explicitly committed before going out of
         scope)'''
         self._abort()
 
     def _abort(self):
         self.count = 0
         self.usages = 0
         self.file.close()
         self._backupsfile.close()
 
         if self.onabort is not None:
             self.onabort()
 
         try:
             if not self.entries and not self._backupentries:
                 if self.journal:
                     self.opener.unlink(self.journal)
                 if self._backupjournal:
                     self.opener.unlink(self._backupjournal)
                 return
 
             self.report(_("transaction abort!\n"))
 
             try:
                 _playback(self.journal, self.report, self.opener, self._vfsmap,
                           self.entries, self._backupentries, False)
                 self.report(_("rollback completed\n"))
             except Exception:
                 self.report(_("rollback failed - please run hg recover\n"))
         finally:
             self.journal = None
 
 
 def rollback(opener, vfsmap, file, report):
     """Rolls back the transaction contained in the given file
 
     Reads the entries in the specified file, and the corresponding
     '*.backupfiles' file, to recover from an incomplete transaction.
 
     * `file`: a file containing a list of entries, specifying where
     to truncate each file.  The file should contain a list of
     file\0offset pairs, delimited by newlines. The corresponding
     '*.backupfiles' file should contain a list of file\0backupfile
     pairs, delimited by \0.
     """
     entries = []
     backupentries = []
 
     fp = opener.open(file)
     lines = fp.readlines()
     fp.close()
     for l in lines:
         try:
             f, o = l.split('\0')
             entries.append((f, int(o), None))
         except ValueError:
             report(_("couldn't read journal entry %r!\n") % l)
 
     backupjournal = "%s.backupfiles" % file
     if opener.exists(backupjournal):
         fp = opener.open(backupjournal)
         lines = fp.readlines()
         if lines:
             ver = lines[0][:-1]
             if ver == str(version):
                 for line in lines[1:]:
                     if line:
                         # Shave off the trailing newline
                         line = line[:-1]
                         l, f, b, c = line.split('\0')
                         backupentries.append((l, f, b, bool(c)))
             else:
                 report(_("journal was created by a different version of "
                          "Mercurial"))
 
     _playback(file, report, opener, vfsmap, entries, backupentries)