[RFC] git-format-patch: default to --from to avoid spoofed mails?

When git-format-patch formats a patch authored by someone other than yourself, it defaults to filling in the "From:" field of the email from the commit author. If you explicitly pass the --from option, git-format-patch will instead use your own committer identity as the "From:", and then put a "From:" line at the top of the body if the commit author differs. (git-am know to use that as the commit author when applying.)

While git-send-email knows how to change the patch mails to use your own address as "From:" and add a "From:" line to the body for the author, any other tool used to send emails doesn't do that. I've seen more than a few mails sent to various mailing lists and patch review tools with a spoofed "From:" field pointing to the commit author, typically without the knowledge of the author, which can lead to interesting surprises.

I'd like to propose changing the default behavior of git-format-patch to --from (and adding a --from-author option to override, and perhaps a config setting). This will not change the output *except* when formatting patches authored by someone else. git-am and git-send-email both handle the --from format without any issues.

Before I write such a patch: does anyone see a problem with such a change?

- Josh Triplett