Add script to check generated release notes

hack/release-notes/check.sh

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+
+# Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+# or more contributor license agreements. Licensed under the Elastic License 2.0;
+# you may not use this file except in compliance with the Elastic License 2.0.
+
+# Script that helps identifying changes that have been labeled as belonging to certain release version
+# where the corresponding commits are not in the release branch.
+# Its main purpose is to discover missing backports.
+
+set -uo pipefail
+
+WD="$(cd "$(dirname "$0")" || return; pwd)"
+ROOT="$WD/../.."
+
+get-prev-version() {
+    local version=$1
+    git tag | grep -v '-' | grep -B1 "$version" | head -1
+}
+
+list-merged-commits() {
+    local nextVersion=$1
+    local prevVersion=$2
+    git log --pretty=oneline "$prevVersion..$nextVersion" | grep -o "#[0-9]*" | sort
+}
+
+list-release-notes-pr-commits() {
+    local version=$1
+    version=${version#v} # strip v prefix
+    grep -o 'pull}[0-9]*' "$ROOT/docs/release-notes/$version.asciidoc" | sed 's/pull}/#/' | sort
+}
+
+count-release-notes-pr-without-merged-commit() {
+    local nextVersion=$1
+    local prevVersion=$2
+    local grepOpts=${3:-}
+    # shellcheck disable=SC2086
+    diff \
+        <(list-merged-commits "$nextVersion" "$prevVersion") \
+        <(list-release-notes-pr-commits "$nextVersion") \
+        | grep $grepOpts '>'
+}
+
+main() {
+    local nextVersion=$1
+    local prevVersion=${2:-$(get-prev-version "$nextVersion")}
+
+    echo "Compare 'merged PR from $prevVersion to $nextVersion' with 'release-notes/$nextVersion'"
+
+    count=$(count-release-notes-pr-without-merged-commit "$nextVersion" "$prevVersion" -c)
+    if [[ "$count" -eq 0 ]]; then
+        echo "✅ LGTM"
+    else
+        echo "❌ Error: no commit found for the following issues:"
+        count-release-notes-pr-without-merged-commit "$nextVersion" "$prevVersion"
+    fi
+}
+
+main "$@"