dirstate: reset _lastnormal and _lastnormaltime

dirstate: reset _lastnormal and _lastnormaltime

on write, invalidate, and clear

--- a/mercurial/dirstate.py	Wed Mar 23 16:06:55 2011 +0100
+++ b/mercurial/dirstate.py	Wed Mar 23 11:22:29 2011 +0100
@@ -238,6 +238,8 @@
                 "_ignore"):
             if a in self.__dict__:
                 delattr(self, a)
+        self._lastnormal = set()
+        self._lastnormaltime = None
         self._dirty = False
 
     def copy(self, source, dest):
@@ -414,6 +416,8 @@
             delattr(self, "_dirs")
         self._copymap = {}
         self._pl = [nullid, nullid]
+        self._lastnormal = set()
+        self._lastnormaltime = None
         self._dirty = True
 
     def rebuild(self, parent, files):
@@ -461,6 +465,8 @@
             write(f)
         st.write(cs.getvalue())
         st.rename()
+        self._lastnormal = set()
+        self._lastnormaltime = None
         self._dirty = self._dirtypl = False
 
     def _dirignore(self, f):