Signed git-tag doesn't find default key

Hello,

I did this:

$ git tag -s adp-sign-tag gpg: skipped "Andy Parkins <andyparkins@gmail.com>": secret key not available gpg: signing failed: secret key not available failed to sign the tag with GPG.

I believe the problem is that I have used the comment field in my key's UID definition.

$ gpg --list-keys andy pub 1024D/4F712F6D 2003-08-14 uid Andy Parkins (Google) <andyparkins@gmail.com>

So when git-tag looks for "Andy Parkins <andyparkins@gmail.com>"; it's not found. The answer is (I think) to search only on the email address when looking for a key. I've simply changed git-tag to have

username=$(git-repo-config user.email)

However, this is clearly wrong as what it actually wants is the committer email. Am I safe to simply process the $tagger variable to extract it?

Andy