To libify `git apply` functionality we have to signal errors to the
caller instead of die()ing. Let's do that by returning -1 instead of
die()ing in read_patch_file().
Helped-by: Stefan Beller <sbeller@google.com> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>