dirstate: move the _dirfoldmap to dirstatemap

Now that dirstatemap is the source of truth for the list of directories, let's
move _dirfoldmap on to it.

This pattern of moving cached variables onto the dirstate map makes it easier to
invalidate them, as seen by how the cache invalidation functions are slowly
shrinking to just be recreating the dirstatemap instance.

Differential Revision: https://phab.mercurial-scm.org/D983

contrib/perf.py

@@ -560,8 +560,8 b' def perfdirfoldmap(ui, repo, **opts):'
     dirstate = repo.dirstate
     'a' in dirstate
     def d():
-        dirstate._dirfoldmap.get('a')
-        del dirstate._dirfoldmap
+        dirstate._map.dirfoldmap.get('a')
+        del dirstate._map.dirfoldmap
         del dirstate._map.dirs
     timer(d)
     fm.end()

mercurial/dirstate.py

@@ -132,14 +132,6 b' class dirstate(object):'
         self._read()
         return self._map
 
-    @propertycache
-    def _dirfoldmap(self):
-        f = {}
-        normcase = util.normcase
-        for name in self._map.dirs:
-            f[normcase(name)] = name
-        return f
-
     @property
     def _sparsematcher(self):
         """The matcher for the sparse checkout.
@@ -372,8 +364,7 b' class dirstate(object):'
         rereads the dirstate. Use localrepo.invalidatedirstate() if you want to
         check whether the dirstate has changed before rereading it.'''
 
-        for a in ("_map", "_dirfoldmap", "_branch",
-                  "_ignore"):
+        for a in ("_map", "_branch", "_ignore"):
             if a in self.__dict__:
                 delattr(self, a)
         self._lastnormaltime = 0
@@ -568,7 +559,7 b' class dirstate(object):'
         normed = util.normcase(path)
         folded = self._map.filefoldmap.get(normed, None)
         if folded is None:
-            folded = self._dirfoldmap.get(normed, None)
+            folded = self._map.dirfoldmap.get(normed, None)
         if folded is None:
             if isknown:
                 folded = path
@@ -576,7 +567,7 b' class dirstate(object):'
                 # store discovered result in dirfoldmap so that future
                 # normalizefile calls don't start matching directories
                 folded = self._discoverpath(path, normed, ignoremissing, exists,
-                                            self._dirfoldmap)
+                                            self._map.dirfoldmap)
         return folded
 
     def normalize(self, path, isknown=False, ignoremissing=False):
@@ -875,7 +866,7 b' class dirstate(object):'
                 if len(paths) > 1:
                     for path in paths:
                         folded = self._discoverpath(path, norm, True, None,
-                                                    self._dirfoldmap)
+                                                    self._map.dirfoldmap)
                         if path != folded:
                             results[path] = None
 
@@ -1396,3 +1387,10 b' class dirstatemap(object):'
         self.read()
         return self.identity
 
+    @propertycache
+    def dirfoldmap(self):
+        f = {}
+        normcase = util.normcase
+        for name in self.dirs:
+            f[normcase(name)] = name
+        return f