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.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-tag.txt

@@ -10,19 +10,27 @@ git-tag -  Create a tag object signed with GPG
 
 SYNOPSIS
 --------
-'git-tag' [-s | -a] [-f] <name>
+'git-tag' [-a | -s | -u <key-id>] [-f] [-m <msg>] <name>
 
 DESCRIPTION
 -----------
-Adds a "tag" reference in .git/refs/tags/
+Adds a 'tag' reference in .git/refs/tags/
 
-Unless "-f" is given, the tag must not yet exist in ".git/refs/tags"
+Unless `-f` is given, the tag must not yet exist in
+`.git/refs/tags/` directory.
 
-If "-s" or "-a" is passed, the user will be prompted for a tag message.
-and a tag object is created.  Otherwise just the SHA1 object
-name of the commit object is written.
+If one of `-a`, `-s`, or `-u <key-id>` is passed, the command
+creates a 'tag' object, and requires the tag message.  Unless
+`-m <msg>` is given, an editor is started for the user to type
+in the tag message.
 
-A GnuPG signed tag object will be created when "-s" is used.
+Otherwise just the SHA1 object name of the commit object is
+written (i.e. an lightweight tag).
+
+A GnuPG signed tag object will be created when `-s` or `-u
+<key-id>` is used.  When `-u <key-id>` is not used, the
+committer identity for the current user is used to find the
+GnuPG key for signing.
 
 
 Author

git-tag.sh

@@ -4,7 +4,7 @@
 . git-sh-setup || die "Not a git archive"
 
 usage () {
-    echo >&2 "Usage: git-tag [-a | -s] [-f] [-m "tag message"] tagname"
+    echo >&2 "Usage: git-tag [-a | -s | -u <key-id>] [-f] [-m <msg>] <tagname>"
     exit 1
 }
 
@@ -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="$1"
+	;;
     -*)
         usage
 	;;
@@ -50,6 +57,7 @@ shift
 object=$(git-rev-parse --verify --default HEAD "$@") || exit 1
 type=$(git-cat-file -t $object) || exit 1
 tagger=$(git-var GIT_COMMITTER_IDENT) || exit 1
+: ${username:=$(expr "$tagger" : '\(.*>\)')}
 
 trap 'rm -f .tmp-tag* .tagmsg .editmsg' 0
 
@@ -65,13 +73,15 @@ if [ "$annotate" ]; then
 
     grep -v '^#' < .editmsg | git-stripspace > .tagmsg
 
-    [ -s .tagmsg ] || exit
+    [ -s .tagmsg ] || {
+	echo >&2 "No tag message?"
+	exit 1
+    }
 
     ( 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 "$me" .tmp-tag &&
+	gpg -bsa -u "$username" .tmp-tag &&
 	cat .tmp-tag.asc >>.tmp-tag ||
 	die "failed to sign the tag with GPG."
     fi