diff -r a585d78e7b2f -r bc0778f5619a mercurial/bundlerepo.py
--- a/mercurial/bundlerepo.py	Wed Nov 30 22:43:24 2011 -0600
+++ b/mercurial/bundlerepo.py	Thu Dec 01 14:17:17 2011 +0100
@@ -266,6 +266,10 @@
     def getcwd(self):
         return os.getcwd() # always outside the repo
 
+    def _writebranchcache(self, branches, tip, tiprev):
+        # don't overwrite the disk cache with bundle-augmented data
+        pass
+
 def instance(ui, path, create):
     if create:
         raise util.Abort(_('cannot create new bundle repository'))