branchcache: don't verify all nodes while writing

nodes are verified either when they are added or used. In case of commits. we
will load the whole branchmap, only verify nodes for the branch on which we are
committing and then we write.

However before this patch, writing the branchmap was validating all the nodes
whereas it should not. This patch fixes that.

Differential Revision: https://phab.mercurial-scm.org/D6290

mercurial/branchmap.py

@@ -341,7 +341,7 b' class branchcache(object):'
                 cachekey.append(hex(self.filteredhash))
             f.write(" ".join(cachekey) + '\n')
             nodecount = 0
-            for label, nodes in sorted(self.iteritems()):
+            for label, nodes in sorted(self._entries.iteritems()):
                 label = encoding.fromlocal(label)
                 for node in nodes:
                     nodecount += 1