Badly formatted commits may have very long comments. This causes
git-format-patch to fail. To avoid that, truncate the filename
to a value we believe will always work.
Err out if the patch file cannot be created.
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com> Acked-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Junio C Hamano <junkio@cox.net>