revset: make heads(commonancestors(x + x^)) be x^, not x

Differential Revision: https://phab.mercurial-scm.org/D4742

mercurial/revset.py

@@ -614,11 +614,11 b' def _commonancestorheads(repo, subset, x'
     # This is an internal method is for quickly calculating "heads(::x and
     # ::y)"
 
-    # These greatest common ancestors are the same ones that the consesus bid
+    # These greatest common ancestors are the same ones that the consensus bid
     # merge will find.
-    h = heads(repo, fullreposet(repo), x, anyorder)
+    startrevs = getset(repo, fullreposet(repo), x, order=anyorder)
 
-    ancs = repo.changelog._commonancestorsheads(*list(h))
+    ancs = repo.changelog._commonancestorsheads(*list(startrevs))
     return subset & baseset(ancs)
 
 @predicate('commonancestors(set)', safe=True)

tests/test-revset.t

@@ -1080,7 +1080,7 b' test the specialized implementation of h'
   $ hg log -T '{rev}\n' -r 'heads(commonancestors(9))'
   9
   $ hg log -T '{rev}\n' -r 'heads(commonancestors(8 + 9))'
-  9
+  8
 
 test ancestor variants of empty revision