dirstate: avoid match.files() in walk()

mercurial/dirstate.py

@@ -759,7 +759,7 b' class dirstate(object):'
         if match.isexact(): # match.exact
             exact = True
             dirignore = util.always # skip step 2
-        elif match.files() and not match.anypats(): # match.match, no patterns
+        elif match.prefix(): # match.match, no patterns
             skipstep3 = True
 
         if not exact and self._checkcase: