no-conflict-markers.yml

# https://stackoverflow.com/a/76322606
name: No unresolved conflicts
on:
  pull_request:
    branches: [ master ]
jobs:
  detect-unresolved-conflicts:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: List files with merge conflict markers
        run: git --no-pager grep "<<<<<<<" ":(exclude).github/" || true
      - name: Fail or succeed job if any files with merge conflict markers have been checked in
        # Find lines containing "<<<<<<<", then count the number of lines.
        # 0 matching lines results in exit code 0, i.e. success.
        run: exit $(git grep "<<<<<<<" ":(exclude).github/" | wc --lines)