[PATCH 5 of 5 v6] revset: use faster branchcache branchfast function without autoload and close

[Mads Kiilerich]

# HG changeset patch
# User Mads Kiilerich <madski at unity3d.com>
# Date 1413657790 -7200
#      Sat Oct 18 20:43:10 2014 +0200
# Node ID 60419932a5a7ff04a4c5f396d778b489d41a62e9
# Parent  16f60e8b47b29373d18d74ab35e673aef3aebfa5
revset: use faster branchcache branchfast function without autoload and close

This gives some code duplication, but perfrevset 'branch(mobile)' on
mozilla-central shows 10% improvement:
Before:
! wall 0.659279 comb 0.660000 user 0.660000 sys 0.000000 (best of 15)
After:
! wall 0.605124 comb 0.610000 user 0.610000 sys 0.000000 (best of 17)

diff --git a/mercurial/branchmap.py b/mercurial/branchmap.py
--- a/mercurial/branchmap.py
+++ b/mercurial/branchmap.py
@@ -396,6 +396,22 @@ class revbranchcache(object):
 
         return self.branchinfo(rev)[0]
 
+    def branchfast(self, rev):
+        """Return branch name for rev, using and updating persistent cache.
+        The cache must be loaded first."""
+        node = self._repo.changelog.node(rev)
+        cachenode, branchidx = struct.unpack_from(bcrecfmt, self._records,
+                                                  rev * bcrecsize)
+        branchidx &= bcbranchidxmask
+        if cachenode == node and branchidx < len(self._nameslocal):
+            b = self._nameslocal[branchidx]
+            if b:
+                return b
+            b = encoding.tolocal(self._namesutf8[branchidx])
+            self._nameslocal[branchidx] = b
+            return b
+        return self.branchinfo(rev)[0]
+
     def save(self):
         """Save branch cache if it is dirty."""
         if self._dirty:
diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -478,7 +478,8 @@ def branch(repo, subset, x):
     a regular expression. To match a branch that actually starts with `re:`,
     use the prefix `literal:`.
     """
-    branch = repo.revbranchcache.branch
+    branch = repo.revbranchcache.load()
+    branch = repo.revbranchcache.branchfast
     try:
         b = getstring(x, '')
     except error.ParseError: