--- a/mercurial/localrepo.py	Tue Feb 01 17:53:50 2011 -0600
+++ b/mercurial/localrepo.py	Mon Jan 17 09:37:20 2011 +0100
@@ -439,7 +439,7 @@
     def _readbranchcache(self):
         partial = {}
         try:
-            f = self.opener(os.path.join("cache", "branchheads"))
+            f = self.opener("cache/branchheads")
             lines = f.read().split('\n')
             f.close()
         except (IOError, OSError):
@@ -467,8 +467,7 @@
 
     def _writebranchcache(self, branches, tip, tiprev):
         try:
-            f = self.opener(os.path.join("cache", "branchheads"), "w",
-                            atomictemp=True)
+            f = self.opener("cache/branchheads", "w", atomictemp=True)
             f.write("%s %s\n" % (hex(tip), tiprev))
             for label, nodes in branches.iteritems():
                 for node in nodes: