Fix hash generation after switching to "git show"

When I switched to "git show" I didn't fully test whether it would
generate the same patchwork hashes as "git diff" proper. The few sample
tries I ran happened to do the right thing, but many other commits would
generate different hashes. Make sure we ignore anything that comes
before we find "diff " on the line.

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
1 file changed