dirstate: split the foldmap into separate ones for files and directories

Computing the set of directories in the dirstate can be pretty expensive. For
'hg status' without arguments, it turns out we actually never need to figure
out the right case for directories in the foldmap. (An upcoming patch explains
why.)

This patch splits up the directory and file maps into separate ones, allowing
for the subsequent optimization in status.

mercurial/dirstate.py

@@ -87,15 +87,21 b' class dirstate(object):'
         return self._copymap
 
     @propertycache
-    def _foldmap(self):
+    def _filefoldmap(self):
         f = {}
         normcase = util.normcase
         for name, s in self._map.iteritems():
             if s[0] != 'r':
                 f[normcase(name)] = name
+        f['.'] = '.' # prevents useless util.fspath() invocation
+        return f
+
+    @propertycache
+    def _dirfoldmap(self):
+        f = {}
+        normcase = util.normcase
         for name in self._dirs:
             f[normcase(name)] = name
-        f['.'] = '.' # prevents useless util.fspath() invocation
         return f
 
     @repocache('branch')
@@ -332,8 +338,8 b' class dirstate(object):'
             self._pl = p
 
     def invalidate(self):
-        for a in ("_map", "_copymap", "_foldmap", "_branch", "_pl", "_dirs",
-                "_ignore"):
+        for a in ("_map", "_copymap", "_filefoldmap", "_dirfoldmap", "_branch",
+                  "_pl", "_dirs", "_ignore"):
             if a in self.__dict__:
                 delattr(self, a)
         self._lastnormaltime = 0
@@ -492,24 +498,27 b' class dirstate(object):'
 
     def _normalizefile(self, path, isknown, ignoremissing=False, exists=None):
         normed = util.normcase(path)
-        folded = self._foldmap.get(normed, None)
+        folded = self._filefoldmap.get(normed, None)
         if folded is None:
             if isknown:
                 folded = path
             else:
                 folded = self._discoverpath(path, normed, ignoremissing, exists,
-                                            self._foldmap)
+                                            self._filefoldmap)
         return folded
 
     def _normalize(self, path, isknown, ignoremissing=False, exists=None):
         normed = util.normcase(path)
-        folded = self._foldmap.get(normed, None)
+        folded = self._filefoldmap.get(normed,
+                                       self._dirfoldmap.get(normed, None))
         if folded is None:
             if isknown:
                 folded = path
             else:
+                # store discovered result in dirfoldmap so that future
+                # normalizefile calls don't start matching directories
                 folded = self._discoverpath(path, normed, ignoremissing, exists,
-                                            self._foldmap)
+                                            self._dirfoldmap)
         return folded
 
     def normalize(self, path, isknown=False, ignoremissing=False):