contrib/subtree: fix "subtree split" skipped-merge bug

'git subtree split' can incorrectly skip a merge even when both parents
act on the subtree, provided the merge results in a tree identical to
one of the parents. Fix by copying the merge if at least one parent is
non-identical, and the non-identical parent is not an ancestor of the
identical parent.

Also, add a test case which checks that a descendant remains a
descendent on the subtree in this case.

Signed-off-by: Dave Ware <davidw@realtimegenomics.com>
Reviewed-by: David A. Greene <greened@obbligato.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions