Stupid git question: adding acked-by

[Jerry Van Baren <gvb.linuxppc.dev@gmail.com>]

OK git gurus, this is something I have not figured out: the best way to 
add acked-by (or additional signed-off-by) lines to git patches.

What I'm talking about is when I've applied a patch to my repo and 
published the change on the list and get an "acked-by" back.  By the 
time I get the ack, the acked patch may be several patches deep.  My 
current technique is to reset the repo, edit the patch(es) to add the 
"acked-by" lines, and then re-apply the patches.  PITA and probably the 
stupidest way.

Stacked git should work (effectively does the same thing but more 
gracefully), but I have not gone that route yet.

There must be a better way, if only I could find the right (of 137) 
git-* command...

Hints, please?

Thanks,
gvb