dirstate: factor out code to discover normalized path

In upcoming patches we're going to reuse this code. The storemap is currently
always the foldmap, but will vary in future patches.

mercurial/dirstate.py

@@ -464,20 +464,14 class dirstate(object):
             self._droppath(f)
             del self._map[f]
 
-    def _normalize(self, path, isknown, ignoremissing=False, exists=None):
-        normed = util.normcase(path)
-        folded = self._foldmap.get(normed, None)
-        if folded is None:
-            if isknown:
-                folded = path
-            else:
+    def _discoverpath(self, path, normed, ignoremissing, exists, storemap):
                 if exists is None:
                     exists = os.path.lexists(os.path.join(self._root, path))
                 if not exists:
                     # Maybe a path component exists
                     if not ignoremissing and '/' in path:
                         d, f = path.rsplit('/', 1)
-                        d = self._normalize(d, isknown, ignoremissing, None)
+                d = self._normalize(d, False, ignoremissing, None)
                         folded = d + "/" + f
                     else:
                         # No path components, preserve original case
@@ -487,13 +481,24 class dirstate(object):
                     # against dirstate
                     if '/' in normed:
                         d, f = normed.rsplit('/', 1)
-                        d = self._normalize(d, isknown, ignoremissing, True)
+                d = self._normalize(d, False, ignoremissing, True)
                         r = self._root + "/" + d
                         folded = d + "/" + util.fspath(f, r)
                     else:
                         folded = util.fspath(normed, self._root)
-                    self._foldmap[normed] = folded
+            storemap[normed] = folded
+
+        return folded
 
+    def _normalize(self, path, isknown, ignoremissing=False, exists=None):
+        normed = util.normcase(path)
+        folded = self._foldmap.get(normed, None)
+        if folded is None:
+            if isknown:
+                folded = path
+            else:
+                folded = self._discoverpath(path, normed, ignoremissing, exists,
+                                            self._foldmap)
         return folded
 
     def normalize(self, path, isknown=False, ignoremissing=False):