Oftentimes, patches created by git format-patch will be stored in
version control or compared with diff. In these cases, two otherwise
identical patches can have different commit hashes, leading to diff
noise. Teach git format-patch a --zero-commit option that instead
produces an all-zero hash to avoid this diff noise.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>