diff -r 952baa2f3325 -r 5ccdca7df211 mercurial/localrepo.py
--- a/mercurial/localrepo.py	Sun Jan 16 17:26:34 2011 +0100
+++ b/mercurial/localrepo.py	Tue Jan 04 06:29:08 2011 +0100
@@ -439,7 +439,7 @@
     def _readbranchcache(self):
         partial = {}
         try:
-            f = self.opener("branchheads.cache")
+            f = self.opener(os.path.join("cache", "branchheads"))
             lines = f.read().split('\n')
             f.close()
         except (IOError, OSError):
@@ -467,7 +467,8 @@
 
     def _writebranchcache(self, branches, tip, tiprev):
         try:
-            f = self.opener("branchheads.cache", "w", atomictemp=True)
+            f = self.opener(os.path.join("cache", "branchheads"), "w",
+                            atomictemp=True)
             f.write("%s %s\n" % (hex(tip), tiprev))
             for label, nodes in branches.iteritems():
                 for node in nodes: