sample update-hook: sanely handle a new branch head.

Instead of showing all the history since the beginning of time
leading to the the branch head, show only the changes this new
branch brings to the world.

This originally came from Linus and tested by Andreas Ericsson.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

templates/hooks--update

@@ -68,7 +68,7 @@ then
 	refs/heads/*)
 		branch="${1##refs/heads/}"
 		echo "New branch '$branch' available with the following commits:"
-		git-rev-list --pretty "$3"
+		git-rev-list --pretty "$3" $(git-rev-parse --not --all)
 		;;
 	esac
 else