localrepo: avoid unnecessary sorting

headrevs output already sorted, no need to sort it again.

mercurial/localrepo.py

@@ -1854,7 +1854,7 b' class localrepository(object):'
     def heads(self, start=None):
         if start is None:
             cl = self.changelog
-            headrevs = sorted(cl.headrevs(), reverse=True)
+            headrevs = reversed(cl.headrevs())
             return [cl.node(rev) for rev in headrevs]
 
         heads = self.changelog.heads(start)