RFE: git-patch-id should handle patches without leading "diff"

Hi, all:

Every now and again I come across a patch sent to LKML without a leading "diff a/foo b/foo" -- usually produced by quilt. E.g.:

https://lore.kernel.org/lkml/20181125185004.151077005@linutronix.de/

I am guessing quilt does not bother including the leading "diff a/foo b/foo" because it's redundant with the next two lines, however this remains a valid patch recognized by git-am.

If you pipe that patch via git-patch-id, it produces nothing, but if I put in the leading "diff", like so:

diff a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c

then it properly returns "fb3ae17451bc619e3d7f0dd647dfba2b9ce8992e".

Can we please teach git-patch-id to work without the leading diff a/foo b/foo, same as git-am?

Best, -K