Make "git tag" more user-friendly

Instead of having to cut-and-paste the result, write it to the tag
directory directly.  Also, start an editor for the tag message, rather
than just reading it from stdin.

git-tag-script

 #!/bin/sh
 # Copyright (c) 2005 Linus Torvalds
 
-: ${GIT_DIR=.git}
+. git-sh-setup-script || die "Not a git archive"
+name="$1"
+[ "$name" ] || die "I need a tag-name"
 
 object=${2:-$(cat "$GIT_DIR"/HEAD)}
 type=$(git-cat-file -t $object) || exit 1
-( echo -e "object $object\ntype $type\ntag $1\n"; cat ) > .tmp-tag
-rm -f .tmp-tag.asc
+
+( echo "#"
+  echo "# Write a tag message"
+  echo "#" ) > .editmsg
+${VISUAL:-${EDITOR:-vi}} .editmsg || exit
+
+grep -v '^#' < .editmsg | git-stripspace > .tagmsg
+
+[ -s .tagmsg ] || exit
+
+( echo -e "object $object\ntype $type\ntag $name\n"; cat .tagmsg ) > .tmp-tag
+rm -f .tmp-tag.asc .tagmsg
 gpg -bsa .tmp-tag && cat .tmp-tag.asc >> .tmp-tag
-git-mktag < .tmp-tag
+git-mktag < .tmp-tag > "$GIT_DIR/refs/tags/$name"
 #rm .tmp-tag .tmp-tag.sig