Update git helper usage

buildroot/share/git/mfpr

@@ -1,11 +1,11 @@
 #!/usr/bin/env bash
 #
-# mfpr [1|2]
+# mfpr [1|2|3]
 #
 # Make a PR against bugfix-1.1.x or bugfix-2.0.x
 #
 
-[[ $# < 2 && $1 != "-h" && $1 != "--help" ]] || { echo "usage: `basename $0` [branch]" 1>&2 ; exit 1; }
+[[ $# < 2 && $1 != "-h" && $1 != "--help" ]] || { echo "usage: `basename $0` [1|2|3] [branch]" 1>&2 ; exit 1; }
 
 MFINFO=$(mfinfo "$@") || exit 1
 IFS=' ' read -a INFO <<< "$MFINFO"