ci: Add guardrails for release backporting (#8449)

.github/scripts/releasing/check-no-copied-release-commits.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+
+# Exit the script as soon as an error occurs.
+set -euo pipefail
+
+# This script fails if the commits in <base>..<head> copy commits from a release or staging branch
+# (e.g. by rebasing or cherry-picking them) instead of merging that branch, see RELEASING.md.
+# Commits are compared by patch-id,
+# and only against release and staging commits that <head> does not already contain.
+# Usage: .github/scripts/releasing/check-no-copied-release-commits.sh <base> <head>
+
+if [ "$#" -ne 2 ]; then
+    echo "Usage: $0 <base> <head>"
+    exit 1
+fi
+
+BASE=$1
+HEAD=$2
+
+patch_ids() {
+    git log --no-merges --patch --no-color --no-ext-diff "$@" | git patch-id --stable | sort
+}
+
+mapfile -t BRANCHES < <(git for-each-ref --format='%(refname)' 'refs/remotes/*/release/*' 'refs/remotes/*/staging/*')
+if [ "${#BRANCHES[@]}" -eq 0 ]; then
+    echo "Error: No release or staging branches found."
+    exit 1
+fi
+
+# Each line is "<patch-id> <commit>".
+RELEASE_PATCHES=$(patch_ids "${BRANCHES[@]}" --not "${HEAD}")
+PR_PATCHES=$(patch_ids "${BASE}..${HEAD}")
+
+# Each line is "<patch-id> <release commit> <PR commit>".
+COPIES=$(join <(echo "${RELEASE_PATCHES}") <(echo "${PR_PATCHES}"))
+if [ -z "${COPIES}" ]; then
+    echo "No copied release commits found."
+    exit 0
+fi
+
+echo "These commits copy release commits instead of merging them:"
+while read -r _ RELEASE_COMMIT PR_COMMIT; do
+    echo "  $(git log -1 --format='%h %s' "${PR_COMMIT}") (copies ${RELEASE_COMMIT:0:10})"
+done <<<"${COPIES}"
+echo
+echo "Merge the release tag (or branch) instead, see RELEASING.md."
+exit 1

.github/scripts/releasing/check-releases-merged.sh

@@ -0,0 +1,46 @@
+#!/bin/bash
+
+# Exit the script as soon as an error occurs.
+set -euo pipefail
+
+# This script fails if a final release (a tag like 3.4.0) on a release branch
+# is not merged back into <develop> within a few days, see RELEASING.md.
+# Usage: .github/scripts/releasing/check-releases-merged.sh <develop>
+
+if [ "$#" -ne 1 ]; then
+    echo "Usage: $0 <develop>"
+    exit 1
+fi
+
+DEVELOP=$1
+GRACE_DAYS=3
+
+mapfile -t MERGED_ARGS < <(git for-each-ref --format='--merged=%(refname)' 'refs/remotes/*/release/*')
+if [ "${#MERGED_ARGS[@]}" -eq 0 ]; then
+    echo "Error: No release branches found."
+    exit 1
+fi
+
+# Tags on a release branch that <develop> does not contain.
+TAGS=$(git for-each-ref --format='%(refname:short) %(creatordate:unix)' \
+    "${MERGED_ARGS[@]}" --no-merged="${DEVELOP}" 'refs/tags/[0-9]*')
+
+MISSING=0
+while read -r TAG CREATED; do
+    if ! [[ "${TAG}" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+        continue
+    fi
+    if (($(date +%s) - CREATED < GRACE_DAYS * 86400)); then
+        echo "${TAG}: not merged yet, still within the ${GRACE_DAYS}-day grace period."
+    else
+        echo "${TAG}: not merged into develop."
+        MISSING=1
+    fi
+done <<<"${TAGS}"
+
+if [ "${MISSING}" -ne 0 ]; then
+    echo
+    echo "Merge the missing releases back into develop, see RELEASING.md."
+    exit 1
+fi
+echo "No releases past the grace period are missing from develop."