Print usage on unknown argument

bin/saturnin-push

@@ -11,6 +11,7 @@ while true; do case $1 in
     -o|--order)     ORDER=$2;           shift 2;    ;;
     -h|--help)      usage;                          ;;
     "")             break                           ;;
+    -*)             usage;                          ;;
     *)              hosts="$1"; shift;              ;;
 esac done