Allow "-u" flag to tag signing

From: Linus Torvalds <torvalds@osdl.org>
Date: Oct 6, 2005, 16:58 UTC
Message-ID: <Pine.LNX.4.64.0510060952410.31407@g5.osdl.org>

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.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
Not very well tested, but I re-did my v2.6.14-rc3 tag with this, since I'd 
messed up the comments (and called it v2.6.14-rc2 in there ;)

So it may even work.

diff --git a/git-tag.sh b/git-tag.sh
--- a/git-tag.sh
+++ b/git-tag.sh
@@ -12,6 +12,7 @@ annotate=
 signed=
 force=
 message=
+username=
 while case "$#" in 0) break ;; esac
 do
     case "$1" in
@@ -30,6 +31,12 @@ do
 	shift
 	message="$1"
 	;;
+    -u)
+	annotate=1
+	signed=1
+	shift
+	username="$1"
+	;;
     -*)
         usage
 	;;
@@ -70,8 +77,11 @@ if [ "$annotate" ]; then
     ( echo -e "object $object\ntype $type\ntag $name\ntagger $tagger\n"; cat .tagmsg ) > .tmp-tag
     rm -f .tmp-tag.asc .tagmsg
     if [ "$signed" ]; then
-	me=$(expr "$tagger" : '\(.*>\)') &&
-	gpg -bsa -u "$me" .tmp-tag &&
+	{
+		[ "$username" ] ||
+		username=$(expr "$tagger" : '\(.*>\)')
+	} &&
+	gpg -bsa -u "$username" .tmp-tag &&
 	cat .tmp-tag.asc >>.tmp-tag ||
 	die "failed to sign the tag with GPG."
     fi