Let a command-line --keep-subject (-k) override a config-specified
format.numbered (--numbered (-n)), rather than provoking the
"-n and -k are mutually exclusive" failure.
* t4021-format-patch-numbered.sh: Test for the above
Signed-off-by: NJim Meyering <meyering@redhat.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>