Fail CI if workflow needs regenerating.

.github/workflows/pull-request.yml

@@ -20,11 +20,13 @@ jobs:
           python3 -m pip install --upgrade pip virtualenv
           sudo apt update
           python3 ./mach bootstrap
-      - name: Tidy
-        run: python3 ./mach test-tidy --no-progress --all
+      - name: Workflow check
+        run: ./etc/ci/workflow_changed.sh
       - name: Release build
         run: python3 ./mach build --release
       - name: Unit tests
         run: python3 ./mach test-unit --release
+      - name: Tidy
+        run: python3 ./mach test-tidy --no-progress --all
       - name: Lockfile check
         run: ./etc/ci/lockfile_changed.sh

etc/ci/workflow_changed.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+python3 etc/ci/generate_workflow.py
+
+diff="$(find . -name 'main.yml' -print0 | xargs -0 git diff)"
+echo "${diff}"
+[[ -z "${diff}" ]]