git subtree push does not support --squash, as previously illustrated in
6ccc71a9 (contrib/subtree: there's no push --squash, 2015-05-07)
Signed-off-by: Danny Lin <danny0838@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Please read git-subtree.txt for documentation. Please don't contact me using github mail; it's slow, ugly, and worst of all, redundant. Email me instead at apenwarr@gmail.com and I'll be happy to help. Avery