changelog-label-check.yml

name: Changelog label check
on:
  pull_request:
    types: [labeled, unlabeled]

jobs:
  check:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@master
      with:
        ref: ${{ github.ref }}

    - name: Set up Python
      uses: actions/setup-python@v2
      with:
        python-version: '3.8'
      
    - name: Check changelog label
      run: python .github/workflows/changelog-label-check.py

    - name: Comment
      if: ${{ github.event.action == 'labeled' && contains( github.event.pull_request.labels.*.name, 'changelog/Changed') }}
      uses: actions/github-script@0.3.0
      with:
        github-token: ${{ secrets.GITHUB_TOKEN }}
        script: |
          const { issue: { number: issue_number }, repo: { owner, repo }  } = context;
          github.issues.createComment({ issue_number, owner, repo, body: "Label `changelog/Changed` was added to this Pull Request, so the next release will bump major version. Please make sure this is a breaking change, or use the `changelog/Fixed` label." });