name: Enforce allowed branches for PRs to main

permissions:
  contents: read
on:
  pull_request:
    branches:
      - main

jobs:
  check-branch:
    runs-on: ubuntu-latest
    steps:
      - name: Check PR source branch
        run: |
          echo "Source branch: ${{ github.head_ref }}"
          if [[ "${{ github.head_ref }}" != "documentation" && "${{ github.head_ref }}" != "code" ]]; then
            echo "Error: PRs to main must come from 'documentation' or 'code' branches only."
            exit 1
          fi