Add usage statement to git-checkout.sh

Signed-off-by: Chris Shoemaker <c.shoemaker@cox.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-checkout.sh

@@ -1,6 +1,10 @@
 #!/bin/sh
 . git-sh-setup || die "Not a git archive"
 
+usage () {
+    die "usage: git checkout [-f] [-b <new_branch>] [<branch>] [<paths>...]"
+}
+
 old=$(git-rev-parse HEAD)
 new=
 force=
@@ -26,6 +30,9 @@ while [ "$#" != "0" ]; do
 	--)
 		break
 		;;
+	-*)
+		usage
+		;;
 	*)
 		if rev=$(git-rev-parse --verify "$arg^0" 2>/dev/null)
 		then