git log filtering

I was curious to know what is the easiest way to filter info inside a commit message.

For example say I wanted to find out what patches Joe User has submitted to the git project. I know I can do something like ' git log |grep -B2 "^Author: Joe User" ' and it will output the matches and the commit id. However, if I wanted to filter on something like "Signed-off-by: Joe User", then it is a little harder to dig for the commit id.

Is there a better way of doing this? Or should I accept the fact that git wasn't designed to filter info like this very quickly?

I guess what I was looking to do was embed some metadata inside the commit message and parse through it at a later time (ie like a bugzilla number or something).

Any thoughts/tips/tricks would be helpful.

Cheers, Don