bundlerepo: use _cacheabletip mechanism in bundlerepo

Instead of preventing any cache write we allow writing cache for all content of
the original repo.

The motivation for this change is to drop the custom _writebranchcache of
bundlerepo to help extraction of the branchmap logic out of localrepo.

mercurial/bundlerepo.py

@@ -32,6 +32,7 b' class bundlerevlog(revlog.revlog):'
         self.bundle = bundle
         self.basemap = {}
         n = len(self)
+        self.disktiprev = n - 1
         chain = None
         self.bundlenodes = []
         while True:
@@ -284,9 +285,11 b' class bundlerepository(localrepo.localre'
     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 _cacheabletip(self):
+        # we should not cache data from the bundle on disk
+        ret = super(bundlerepository, self)._cacheabletip()
+        return min(self.changelog.disktiprev, ret)
+
 
 def instance(ui, path, create):
     if create: