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/discovery.py	Sat May 12 00:19:30 2012 +0200
+++ b/mercurial/discovery.py	Sat May 12 00:24:07 2012 +0200
@@ -105,7 +105,7 @@
     og.commonheads, _any, _hds = commoninc
 
     # compute outgoing
-    if not repo._phaseroots[phases.secret]:
+    if not repo._phasecache.phaseroots[phases.secret]:
         og.missingheads = onlyheads or repo.heads()
     elif onlyheads is None:
         # use visible heads as it should be cached