According to POSIX, tv_sec is supposed to be a time_t, but OpenBSD
(and FreeBSD, too) defines it to be a long, which triggers a type
mismatch when a pointer to it is given to localtime_r().
Acked-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>