We want to separate the options relevant to the expiry machinery from
the options affecting the expiration policy. So add a "flags" argument
to expire_reflog() to hold the former.
The argument doesn't yet do anything.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Reviewed-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>