diff -r 5ff1fc726848 -r c6bca38c1cbf eggs/mercurial-1.7.3-py2.6-linux-x86_64.egg/mercurial/transaction.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/eggs/mercurial-1.7.3-py2.6-linux-x86_64.egg/mercurial/transaction.py	Sat Jan 08 11:20:57 2011 +0530
@@ -0,0 +1,176 @@
+# transaction.py - simple journalling 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 <mpm@selenic.com>
+#
+# 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, errno
+import error
+
+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, entries, unlink=True):
+    for f, o, ignore in entries:
+        if o or not unlink:
+            try:
+                opener(f, 'a').truncate(o)
+            except IOError:
+                report(_("failed to truncate %s\n") % f)
+                raise
+        else:
+            try:
+                fn = opener(f).name
+                os.unlink(fn)
+            except (IOError, OSError), inst:
+                if inst.errno != errno.ENOENT:
+                    raise
+    os.unlink(journal)
+
+class transaction(object):
+    def __init__(self, report, opener, journal, after=None, createmode=None):
+        self.count = 1
+        self.usages = 1
+        self.report = report
+        self.opener = opener
+        self.after = after
+        self.entries = []
+        self.map = {}
+        self.journal = journal
+        self._queue = []
+
+        self.file = open(self.journal, "w")
+        if createmode is not None:
+            os.chmod(self.journal, createmode & 0666)
+
+    def __del__(self):
+        if self.journal:
+            self._abort()
+
+    @active
+    def startgroup(self):
+        self._queue.append([])
+
+    @active
+    def endgroup(self):
+        q = self._queue.pop()
+        d = ''.join(['%s\0%d\n' % (x[0], x[1]) for x in q])
+        self.entries.extend(q)
+        self.file.write(d)
+        self.file.flush()
+
+    @active
+    def add(self, file, offset, data=None):
+        if file in self.map:
+            return
+        if self._queue:
+            self._queue[-1].append((file, offset, data))
+            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 find(self, file):
+        if file in self.map:
+            return self.entries[self.map[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
+
+    @active
+    def close(self):
+        '''commit the transaction'''
+        self.count -= 1
+        if self.count != 0:
+            return
+        self.file.close()
+        self.entries = []
+        if self.after:
+            self.after()
+        if os.path.isfile(self.journal):
+            os.unlink(self.journal)
+        self.journal = None
+
+    @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()
+
+        try:
+            if not self.entries:
+                if self.journal:
+                    os.unlink(self.journal)
+                return
+
+            self.report(_("transaction abort!\n"))
+
+            try:
+                _playback(self.journal, self.report, self.opener,
+                          self.entries, False)
+                self.report(_("rollback completed\n"))
+            except:
+                self.report(_("rollback failed - please run hg recover\n"))
+        finally:
+            self.journal = None
+
+
+def rollback(opener, file, report):
+    entries = []
+
+    for l in open(file).readlines():
+        f, o = l.split('\0')
+        entries.append((f, int(o), None))
+
+    _playback(file, report, opener, entries)