diff -r 88a448a12ae8 -r 751639bf6fc4 mercurial/cmdutil.py
--- a/mercurial/cmdutil.py	Mon Nov 21 22:17:45 2016 -0500
+++ b/mercurial/cmdutil.py	Mon Nov 21 21:29:32 2016 -0500
@@ -27,6 +27,7 @@
     changelog,
     copies,
     crecord as crecordmod,
+    dirstateguard as dirstateguardmod,
     encoding,
     error,
     formatter,
@@ -3521,57 +3522,4 @@
         hint = after[0]
     raise error.Abort(_('no %s in progress') % task, hint=hint)
 
-class dirstateguard(object):
-    '''Restore dirstate at unexpected failure.
-
-    At the construction, this class does:
-
-    - write current ``repo.dirstate`` out, and
-    - save ``.hg/dirstate`` into the backup file
-
-    This restores ``.hg/dirstate`` from backup file, if ``release()``
-    is invoked before ``close()``.
-
-    This just removes the backup file at ``close()`` before ``release()``.
-    '''
-
-    def __init__(self, repo, name):
-        self._repo = repo
-        self._active = False
-        self._closed = False
-        self._suffix = '.backup.%s.%d' % (name, id(self))
-        repo.dirstate.savebackup(repo.currenttransaction(), self._suffix)
-        self._active = True
-
-    def __del__(self):
-        if self._active: # still active
-            # this may occur, even if this class is used correctly:
-            # for example, releasing other resources like transaction
-            # may raise exception before ``dirstateguard.release`` in
-            # ``release(tr, ....)``.
-            self._abort()
-
-    def close(self):
-        if not self._active: # already inactivated
-            msg = (_("can't close already inactivated backup: dirstate%s")
-                   % self._suffix)
-            raise error.Abort(msg)
-
-        self._repo.dirstate.clearbackup(self._repo.currenttransaction(),
-                                         self._suffix)
-        self._active = False
-        self._closed = True
-
-    def _abort(self):
-        self._repo.dirstate.restorebackup(self._repo.currenttransaction(),
-                                           self._suffix)
-        self._active = False
-
-    def release(self):
-        if not self._closed:
-            if not self._active: # already inactivated
-                msg = (_("can't release already inactivated backup:"
-                         " dirstate%s")
-                       % self._suffix)
-                raise error.Abort(msg)
-            self._abort()
+dirstateguard = dirstateguardmod.dirstateguard