From patchwork Thu Apr 17 18:08:00 2014
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Subject: [8, of, 9,
 cah] context: tell when .ancestor picks one of multiple common
 ancestors heads
From: Mads Kiilerich <mads@kiilerich.com>
X-Patchwork-Id: 4402
Message-Id: <ba5e0b1e2289a34a3552.1397758080@localhost.localdomain>
To: mercurial-devel@selenic.com
Date: Thu, 17 Apr 2014 20:08:00 +0200

# HG changeset patch
# User Mads Kiilerich <madski@unity3d.com>
# Date 1397748724 -7200
#      Thu Apr 17 17:32:04 2014 +0200
# Node ID ba5e0b1e2289a34a35522d94d7e7b96ba244120d
# Parent  4a6c8b6b10d3690bfc1bb5de789d6ebb475ebb81
context: tell when .ancestor picks one of multiple common ancestors heads

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -402,8 +402,18 @@ class changectx(basectx):
         n2 = c2._node
         if n2 is None:
             n2 = c2._parents[0]._node
-        n = self._repo.changelog.ancestor(self._node, n2)
-        return changectx(self._repo, n)
+        ancs = self._repo.changelog.commonancestorsheads(self._node, n2)
+        if not ancs:
+            anc = nullid
+        elif len(ancs) == 1:
+            anc = ancs[0]
+        else:
+            anc = self._repo.changelog.ancestor(self._node, n2)
+            self._repo.ui.status(
+                _("note: %s is best ancestor of %s and %s, not %s\n") %
+                (short(anc), short(self._node), short(n2),
+                 ' '.join(short(n) for n in sorted(ancs) if n != anc)))
+        return changectx(self._repo, anc)
 
     def descendant(self, other):
         """True if other is descendant of this changeset"""
diff --git a/tests/test-merge-criss-cross.t b/tests/test-merge-criss-cross.t
--- a/tests/test-merge-criss-cross.t
+++ b/tests/test-merge-criss-cross.t
@@ -23,7 +23,9 @@ Criss cross merging
   $ echo '5 second change' > f1
   $ hg ci -m '5 second change f1'
 
-  $ hg up -qr3
+  $ hg up -r3
+  note: 0f6b37dbe527 is best ancestor of adfe50279922 and cf89f02107e5, not 40663881a6dd
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo '6 second change' > f2
   $ hg ci -m '6 second change f2'
 
@@ -72,6 +74,7 @@ Criss cross merging
   
 
   $ hg merge -v --debug --tool internal:dump 5
+  note: 0f6b37dbe527 is best ancestor of 3b08d01b0ab5 and adfe50279922, not 40663881a6dd
     searching for copies back to rev 3
   resolving manifests
    branchmerge: True, force: False, partial: False