branchmap: pass revision insteads of changectx to the update function

Creation of changectx objects is very slow, and they are not very
useful. We are going to drop them. The first step is to change the
function argument type.

mercurial/branchmap.py

@@ -77,8 +77,7 b' def updatecache(repo):'
                 revs.extend(r for  r in extrarevs if r <= partial.tiprev)
     revs.extend(cl.revs(start=partial.tiprev + 1))
     if revs:
-        ctxgen = (repo[r] for r in revs)
-        partial.update(repo, ctxgen)
+        partial.update(repo, revs)
         partial.write(repo)
     assert partial.validfor(repo)
     repo._branchcaches[repo.filtername] = partial
@@ -144,12 +143,13 b' class branchcache(dict):'
             # Abort may be raise by read only opener
             pass
 
-    def update(self, repo, ctxgen):
+    def update(self, repo, revgen):
         """Given a branchhead cache, self, that may have extra nodes or be
         missing heads, and a generator of nodes that are at least a superset of
         heads missing, this function updates self to be correct.
         """
         cl = repo.changelog
+        ctxgen = (repo[r] for r in revgen)
         # collect new branch entries
         newbranches = {}
         for c in ctxgen:

mercurial/discovery.py

@@ -196,7 +196,7 b' def _headssummary(repo, remote, outgoing'
     newmap = branchmap.branchcache((branch, heads[1])
                                  for branch, heads in headssum.iteritems()
                                  if heads[0] is not None)
-    newmap.update(repo, missingctx)
+    newmap.update(repo, (ctx.rev() for ctx in missingctx))
     for branch, newheads in newmap.iteritems():
         headssum[branch][1][:] = newheads
     return headssum

mercurial/localrepo.py

@@ -1406,10 +1406,11 b' class localrepository(object):'
         # it, Otherwise, since nodes were destroyed, the cache is stale and this
         # will be caught the next time it is read.
         if newheadnodes:
-            ctxgen = (self[node] for node in newheadnodes
-                      if self.changelog.hasnode(node))
+            cl = self.changelog
+            revgen = (cl.rev(node) for node in newheadnodes
+                      if cl.hasnode(node))
             cache = self._branchcaches[None]
-            cache.update(self, ctxgen)
+            cache.update(self, revgen)
             cache.write(self)
 
         # Ensure the persistent tag cache is updated.  Doing it now