To libify `git apply` functionality we have to signal errors to the
caller instead of die()ing.
To do that in a compatible manner with the rest of the error handling
in builtin/apply.c, parse_single_patch() should return a negative
integer instead of calling die().
Let's do that by using error() and let's adjust the related test
cases accordingly.
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>