# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 2018-09-26 11:33:09
# Node ID 85a474adaf26d07c408a956c7e5d7d7c0eff072a
# Parent  7a9e2d85f475b1675da537ece26419887f9d8b4e
# Parent  823f34acfd46eb74d362e819d1cc3475bf05bf2f

merge with stable

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -616,30 +616,22 @@ 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)
 def commonancestors(repo, subset, x):
-    """Returns all common ancestors of the set.
-
-    This method is for calculating "::x and ::y" (i.e. all the ancestors that
-    are common to both x and y) in an easy and optimized way. We can't quite
-    use "::head()" because that revset returns "::x + ::y + ..." for each head
-    in the repo (whereas we want "::x *and* ::y").
-
+    """Changesets that are ancestors of every changeset in set.
     """
-    # only wants the heads of the set passed in
-    h = heads(repo, fullreposet(repo), x, anyorder)
-    if not h:
+    startrevs = getset(repo, fullreposet(repo), x, order=anyorder)
+    if not startrevs:
         return baseset()
-    for r in h:
+    for r in startrevs:
         subset &= dagop.revancestors(repo, baseset([r]))
-
     return subset
 
 @predicate('contains(pattern)', weight=100)
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -1049,7 +1049,7 @@ test common ancestors
   2
   4
 
-  $ hg log -T '{rev}\n' -r 'commonancestors(head())'
+  $ hg log -T '{rev}\n' -r 'commonancestors(heads(all()))'
   0
   1
   2
@@ -1063,11 +1063,31 @@ test common ancestors
   8
   9
 
+  $ hg log -T '{rev}\n' -r 'commonancestors(8 + 9)'
+  0
+  1
+  2
+  4
+  8
+
+test the specialized implementation of heads(commonancestors(..))
+(2 gcas is tested in test-merge-criss-cross.t)
+
+  $ hg log -T '{rev}\n' -r 'heads(commonancestors(7 + 9))'
+  4
+  $ hg log -T '{rev}\n' -r 'heads(commonancestors(heads(all())))'
+  4
+  $ hg log -T '{rev}\n' -r 'heads(commonancestors(9))'
+  9
+  $ hg log -T '{rev}\n' -r 'heads(commonancestors(8 + 9))'
+  8
+
 test ancestor variants of empty revision
 
   $ log 'ancestor(none())'
   $ log 'ancestors(none())'
   $ log 'commonancestors(none())'
+  $ log 'heads(commonancestors(none()))'
 
 test ancestors with depth limit