changegroup: cache changelog and manifestlog outside of loop

History has taught us that repo.changelog can add significant overhead
to loops. So cache the changelog instance outside of the loop to
avoid the lookup. While we're here, do the same for manifestlog,
since each loop would otherwise initialize a new manifestlog instance.

mercurial/changegroup.py

@@ -330,11 +330,12 b' class cg1unpacker(object):'
 
                 needfiles = {}
                 if repo.ui.configbool('server', 'validate', default=False):
+                    cl = repo.changelog
+                    ml = repo.manifestlog
                     # validate incoming csets have their manifests
                     for cset in xrange(clstart, clend):
-                        mfnode = repo.changelog.read(
-                            repo.changelog.node(cset))[0]
-                        mfest = repo.manifestlog[mfnode].readdelta()
+                        mfnode = cl.read(cl.node(cset))[0]
+                        mfest = ml[mfnode].readdelta()
                         # store file nodes we must see
                         for f, n in mfest.iteritems():
                             needfiles.setdefault(f, set()).add(n)