util/git-hooks: Check for Signed-off-by line

Enforce the DCO. The logic comes from coreboot's commit-msg hook,
and I've added a pointer to flashrom's development guidelines.

Change-Id: Iea49a06c2d4824be073eff98c8aae1cbc5b145e4
Signed-off-by: David Hendricks <david.hendricks@gmail.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/35295
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed