pull: fix post-pull common computation

Before that changes, pulled revision that happend to be already known locally
(so, not actually added) was not taken into account when computing the new
common set between local and remote.

It appears that we already know the heads of the pulled set. It is in the
`rheads` variable, so we are just using it and everything is works fine.

We are dropping the, now useless, computation of `added` set in the process.

mercurial/localrepo.py

@@ -1670,7 +1670,6 b' class localrepository(object):'
             common, fetch, rheads = tmp
             if not fetch:
                 self.ui.status(_("no changes found\n"))
-                added = []
                 result = 0
             else:
                 tr = self.transaction(trname)
@@ -1696,16 +1695,13 b' class localrepository(object):'
                 # be taken in account for phase synchronization. They may
                 # becomes public and becomes visible again.
                 cl = self.unfiltered().changelog
-                clstart = len(cl)
                 result = self.addchangegroup(cg, 'pull', remote.url())
-                clend = len(cl)
-                added = [cl.node(r) for r in xrange(clstart, clend)]
 
             # compute target subset
             if heads is None:
                 # We pulled every thing possible
                 # sync on everything common
-                subset = common + added
+                subset = common + rheads
             else:
                 # We pulled a specific subset
                 # sync on this subset