Andrew Halberstadt <ahalberstadt@mozilla.com> [Thu, 26 Nov 2015 20:38:31 -0500] rev 1576
evolve: handle merge commit with single obsolete parent (issue4389)
This handles evolving merge commits with a single obsolete parent. Merge
commits with two obsolete parents are still unsupported. Note this depends
on a change to merge.graft in core. Older versions of mercurial will not
have this functionality. Also, test-unstable.t will fail with older
versions.