branchmap: move validity logic in the object itself

In several place, We check if a branchcache is still valid regarding the current
state of the repository. This changeset puts this logic in a method of the object
that can be reused when necessary.

A branch map is considered valid whenever it is up to date or a strict subset of
the repository state.

The change will help making branchcache aware of filtered revision.

The change in keyword is expected. the branch cache is actually invalid after
the amend. The previous check did not detected it.

mercurial/branchmap.py

@@ -9,7 +9,6 b' from node import bin, hex, nullid, nullr'
 import encoding
 
 def read(repo):
-    partial = branchcache()
     try:
         f = repo.opener("cache/branchheads")
         lines = f.read().split('\n')
@@ -20,7 +19,8 b' def read(repo):'
     try:
         last, lrev = lines.pop(0).split(" ", 1)
         last, lrev = bin(last), int(lrev)
-        if lrev >= len(repo) or repo[lrev].node() != last:
+        partial = branchcache(tipnode=last, tiprev=lrev)
+        if not partial.validfor(repo):
             # invalidate the cache
             raise ValueError('invalidating branch cache (tip differs)')
         for l in lines:
@@ -32,8 +32,6 b' def read(repo):'
                 raise ValueError('invalidating branch cache because node '+
                                  '%s does not exist' % node)
             partial.setdefault(label, []).append(bin(node))
-        partial.tipnode = last
-        partial.tiprev = lrev
     except KeyboardInterrupt:
         raise
     except Exception, inst:
@@ -47,12 +45,9 b' def read(repo):'
 def updatecache(repo):
     repo = repo.unfiltered()  # Until we get a smarter cache management
     cl = repo.changelog
-    tip = cl.tip()
     partial = repo._branchcache
-    if partial is not None and partial.tipnode == tip:
-        return
 
-    if partial is None or partial.tipnode not in cl.nodemap:
+    if partial is None or not partial.validfor(repo):
         partial = read(repo)
 
     catip = repo._cacheabletip()
@@ -80,6 +75,17 b' class branchcache(dict):'
         self.tipnode = tipnode
         self.tiprev = tiprev
 
+    def validfor(self, repo):
+        """Is the cache content valide regarding a repo
+
+        - False when cached tipnode are unknown or if we detect a strip.
+        - True when cache is up to date or a subset of current repo."""
+        try:
+            return self.tipnode == repo.changelog.node(self.tiprev)
+        except IndexError:
+            return False
+
+
     def write(self, repo):
         try:
             f = repo.opener("cache/branchheads", "w", atomictemp=True)
@@ -157,12 +163,8 b' class branchcache(dict):'
             if not nodes:
                 droppednodes.extend(nodes)
                 del self[branch]
-        try:
-            node = cl.node(self.tiprev)
-        except IndexError:
-            node = None
-        if ((self.tipnode != node)
-            or (self.tipnode in droppednodes)):
+        if ((not self.validfor(repo)) or (self.tipnode in droppednodes)):
+
             # cache key are not valid anymore
             self.tipnode = nullid
             self.tiprev = nullrev

tests/test-keyword.t

@@ -507,6 +507,7 b' amend'
   $ hg -q commit -d '14 1' -m 'prepare amend'
 
   $ hg --debug commit --amend -d '15 1' -m 'amend without changes' | grep keywords
+  invalidating branch cache (tip differs)
   overwriting a expanding keywords
   $ hg -q id
   67d8c481a6be