rev-list: refuse --first-parent combined with --bisect

rev-list: refuse --first-parent combined with --bisect

rev-list --bisect is used by git bisect, but never together with
--first-parent. Because rev-list --bisect together with --first-parent
is not handled currently, and even leads to segfaults, refuse to use
both options together.

Because this is not supported, it makes little sense to use git log
--bisect --first parent either, because refs/heads/bad is not limited to
the first parent chain.

Helped-by: Junio C. Hamano <gitster@pobox.com>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Kevin Daudt <me@ikke.info>
Signed-off-by: Junio C Hamano <gitster@pobox.com>