Please add a git config option to make --show-signature the default

As stated in title, I'd like to see an option to enable GPG signature by default. I find this feature very useful and would like to enable it by default on my machine, without having to resort to an alias in my ~/.bash_rc.

I asked in #git and checked the git repo, but I didn't see an option listed for this.

Thanks in advance, and for git itself! ;) -Austin