Add a script to upgrade vendor/cmdliner

vendor/update-cmdliner.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+version=1.0.0
+
+set -e -o pipefail
+
+TMP="$(mktemp -d)"
+trap "rm -rf $TMP" EXIT
+
+rm -rf cmdliner
+mkdir -p cmdliner/src
+
+(cd $TMP && opam source cmdliner.$version)
+
+SRC=$TMP/cmdliner.$version
+
+cp -v $SRC/LICENSE.md cmdliner
+cp -v $SRC/src/*.{ml,mli} cmdliner/src
+
+git checkout cmdliner/src/{jbuild,result.ml}
+git add -A .