dirstate.walk: remove subrepo and .hg from results before step 3

An upcoming patch will speed dirstate.walk up by not querying the results dict
when it is empty. This ensures it is in some common cases.

This should be safe because subrepos and .hg aren't part of the dirstate.

mercurial/dirstate.py

@@ -698,6 +698,10 b' class dirstate(object):'
                     elif nf in dmap and matchfn(nf):
                         results[nf] = None
 
+        for s in subrepos:
+            del results[s]
+        del results['.hg']
+
         # step 3: report unseen items in the dmap hash
         if not skipstep3 and not exact:
             visit = sorted([f for f in dmap if f not in results and matchfn(f)])
@@ -725,9 +729,6 b' class dirstate(object):'
                 nf = iter(visit).next
                 for st in util.statfiles([join(i) for i in visit]):
                     results[nf()] = st
-        for s in subrepos:
-            del results[s]
-        del results['.hg']
         return results
 
     def status(self, match, subrepos, ignored, clean, unknown):