name: Prepare documentation PR preview

on:
  pull_request:
    paths:
      - docs/**

jobs:
  pages:
    name: GitHub Pages
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2

      - name: Setup mdbook
        uses: peaceiris/actions-mdbook@4b5ef36b314c2599664ca107bb8c02412548d79d # v1.1.14
        with:
          mdbook-version: '0.4.17'

      - name: Build the documentation
        # mdbook will only create an index.html if we're including docs/README.md in SUMMARY.md.
        # However, we're using docs/README.md for other purposes and need to pick a new page
        # as the default. Let's opt for the welcome page instead.
        run: |
          mdbook build
          cp book/welcome_and_overview.html book/index.html

      - name: Upload Artifact
        uses: actions/upload-artifact@v2
        with:
          name: book
          path: book
          # We'll only use this in a workflow_run, then we're done with it
          retention-days: 1