Add script to update GitSetup from upstream

update-gitsetup.bash

+#!/usr/bin/env bash
+
+set -e
+set -x
+shopt -s dotglob
+
+readonly name="GitSetup"
+readonly ownership="GitSetup Upstream <kwrobot@kitware.com>"
+readonly subtree="GitSetup"
+readonly repo="https://gitlab.kitware.com/utils/gitsetup.git"
+readonly tag="setup"
+readonly shortlog=false
+readonly paths="
+"
+
+extract_source () {
+    git_archive
+}
+
+. "${BASH_SOURCE%/*}/update-third-party.bash"