Ancestor algorithm fix

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Ancestor algorithm fix

The ancestor algorithm was a bit too optimistic about node ordering
still. Add revision numbers to the comparison to sort things out.

manifest hash: f4eaf95057b5623e864359706dcaee820b10fd20
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.0 (GNU/Linux)

iD8DBQFCsTrCywK+sNU5EO8RAtqMAJ9fEJEesPn+0SMg/i/g5vZYmX/pBgCfVnhl
+s88q/Wilw27MVWP6J6oqX8=
=k9AU
-----END PGP SIGNATURE-----

mercurial/revlog.py

@@ -325,10 +325,10 b' class revlog:'
             earliest = self.count()
             while h:
                 d, n = heapq.heappop(h)
-                r = self.rev(n)
                 if n not in seen:
                     seen[n] = 1
-                    yield (-d, n)
+                    r = self.rev(n)
+                    yield (-d, r, n)
                     for p in self.parents(n):
                         heapq.heappush(h, (-dist[p], p))
 
@@ -341,7 +341,7 b' class revlog:'
         # the other, or they match
         while 1:
             if lx == ly:
-                return lx[1]
+                return lx[2]
             elif lx < ly:
                 ly = y.next()
             elif lx > ly: