phases: introduce phasecache The original motivation was changectx.phase() had special logic to correctly lookup in repo._phaserev, including invalidating it when necessary. And at other places, repo._phaserev was accessed directly. This led to the discovery that phases state including _phaseroots, _phaserev and _dirtyphase was manipulated in localrepository.py, phases.py, repair.py, etc. phasecache helps encapsulating that. This patch replaces all phase state in localrepo with phasecache and adjust related code except for advance/retractboundary() in phases. These still access to phasecache internals directly. This will be addressed in a followup.

--- a/mercurial/context.py	Sat May 12 00:19:30 2012 +0200
+++ b/mercurial/context.py	Sat May 12 00:24:07 2012 +0200
@@ -191,12 +191,7 @@
     def bookmarks(self):
         return self._repo.nodebookmarks(self._node)
     def phase(self):
-        if self._rev == -1:
-            return phases.public
-        if self._rev >= len(self._repo._phaserev):
-            # outdated cache
-            del self._repo._phaserev
-        return self._repo._phaserev[self._rev]
+        return self._repo._phasecache.phase(self._repo, self._rev)
     def phasestr(self):
         return phases.phasenames[self.phase()]
     def mutable(self):