Add update script

alma9-base/update.sh

+#!/usr/bin/env bash
+
+set -euo pipefail
+
+THIS_DIR=$(dirname "$0")
+
+function update() {
+    echo "Fetching the latest tag for cern/alma9-base"
+    LATEST_TAG=$(curl -s https://registry.hub.docker.com/v2/repositories/cern/alma9-base/tags/ | grep -oP '"name":\s*"\K(\d{8}-\d+)'| sort -V | tail -n 1)
+    echo "Latest tag is ${LATEST_TAG}"
+    
+    CURRENT_TAG=$(grep -oP "FROM cern/alma9-base:\K[\w.-]+" "${THIS_DIR}/Dockerfile")
+    echo "Current tag is ${CURRENT_TAG}"
+    if [[ "${LATEST_TAG}" == "${CURRENT_TAG}" ]]; then
+        echo "Already on latest image; nothing to do."
+    else
+        echo "Updating Dockerfile to ${LATEST_TAG}"
+        sed -i "s|FROM cern/alma9-base:${CURRENT_TAG}|FROM cern/alma9-base:${LATEST_TAG}|g" "$THIS_DIR/Dockerfile";
+    fi
+}
+
+update