Add and sync actionlint workflow

.github/actions/sync/shared-config.rb

@@ -29,6 +29,7 @@ def git(*args)
 rubocop_yaml = ".rubocop.yml"
 dependabot_yaml = ".github/dependabot.yml"
 docs_workflow_yaml = ".github/workflows/docs.yml"
+actionlint_workflow_yaml = ".github/workflows/actionlint.yml"
 vale_ini = ".vale.ini"
 
 target_gemfile_lock = target_directory_path/"Gemfile.lock"
@@ -98,6 +99,10 @@ def git(*args)
   rubydoc.brew.sh
   ruby-macho
 ].freeze
+custom_actionlint_repos = %w[
+  brew
+  homebrew-core
+]
 rejected_docs_basenames = %w[
   _config.yml
   CNAME
@@ -116,6 +121,7 @@ def git(*args)
   rubocop_yaml,
   dependabot_yaml,
   deprecated_lock_threads,
+  actionlint_workflow_yaml,
   ".github/workflows/stale-issues.yml",
 ].each do |path|
   target_path = target_directory_path/path
@@ -166,6 +172,10 @@ def git(*args)
     next unless docs_path.directory?
 
     FileUtils.cp homebrew_docs_workflow_yaml, target_path
+  when actionlint_workflow_yaml
+    next if custom_actionlint_repos.include?(repository_name)
+
+    FileUtils.cp actionlint_workflow_yaml, target_path
   when vale_ini
     next if custom_docs_repos.include?(repository_name)
 

.github/workflows/actionlint.yml

@@ -0,0 +1,79 @@
+# This file is synced from the `.github` repository, do not modify it directly.
+name: Workflow Syntax
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - '.github/workflows/*.ya?ml'
+  pull_request:
+    paths:
+      - '.github/workflows/*.ya?ml'
+
+defaults:
+  run:
+    shell: bash -xeuo pipefail {0}
+
+concurrency:
+  group: "actionlint-${{ github.ref }}"
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+env:
+  HOMEBREW_DEVELOPER: 1
+  HOMEBREW_NO_AUTO_UPDATE: 1
+  HOMEBREW_NO_ENV_HINTS: 1
+
+permissions: {}
+
+jobs:
+  workflow_syntax:
+    if: github.repository_owner == 'Homebrew'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Homebrew
+        id: setup-homebrew
+        uses: Homebrew/actions/setup-homebrew@master
+        with:
+          core: false
+          cask: false
+          test-bot: false
+
+      - name: Install tools
+        run: brew install actionlint shellcheck zizmor
+
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - run: zizmor --format sarif . >results.sarif
+
+      - name: Upload SARIF file
+        uses: actions/upload-artifact@v4
+        with:
+          name: results.sarif
+          path: results.sarif
+
+      - name: Set up actionlint
+        run: echo "::add-matcher::$(brew --repository)/.github/actionlint-matcher.json"
+
+      - run: actionlint
+
+  upload_sarif:
+    needs: workflow_syntax
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      security-events: write
+    steps:
+      - name: Download SARIF file
+        uses: actions/download-artifact@v4
+        with:
+          name: results.sarif
+          path: results.sarif
+
+      - name: Upload SARIF file
+        uses: github/codeql-action/upload-sarif@v3
+        with:
+          sarif_file: results.sarif
+          category: zizmor