do-not-merge-label-check.yml

# This GitHub Action workflow is triggered on label changes for pull requests.
# When a pull request is labeled with "DO NOT MERGE", the workflow fails, thus
# preventing the pull request from being merged. Otherwise, the workflow will
# succeed, allowing the pull request to be merged.

name: "Check labels that prevent merge"
on:
  pull_request:
    branches: [main]
    types: [labeled, unlabeled]

jobs:
  labels-preventing-merge-check:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        label:
        # Labels that prevent merging
        - 'DO NOT MERGE'
    steps:
      - name: 'Check "${{ matrix.label }}" label'
        run: |
          echo "::notice::Merging permission is diabled for PRs when the '${{ matrix.label }}' label is applied."

          if [ "${{ contains(github.event.pull_request.labels.*.name, matrix.label) }}" = "true" ]; then
            echo "::error::Pull request is labeled as '${{ matrix.label }}'. Please remove the label before merging."
            exit 1
          else
            exit 0
          fi