Re: Allow "-u" flag to tag signing

> The current "git tag -s" thing always uses the tagger name as the signing 
> user key, which is very irritating, since my key is under my email 
> address, but the tagger key obviously contains the actual machine name 
> too.
> 
> Now, I could just use "GIT_COMMITTER_EMAIL" and force it to be my real 
> email, but I actually think that it's nice to see which machine I use for 
> my work. 
> 
> So rather than force my tagger ID to have to match the gpg key name, just 
> support the "-u" flag to "git tag" instead. It implicitly enables signing, 
> since it doesn't make any sense without it. Thus:
> 
> 	git tag -u <gpg-key-name> <tag-name> [<tagged-object>]
> 
> will use the named gpg key for signing.