add build of diff, reset ownership in pr deploy

Author: trevorcampbell

.github/workflows/deploy_pr_preview.yml

@@ -31,6 +31,13 @@ jobs:
           checkName: "Rebuild docker image"
           ref: ${{ github.event.pull_request.head.sha }}
           timeoutSeconds: 60000
+          
+      - name: Get Actions user id
+        id: get_uid
+        run: |
+          actions_user_id=`id -u $USER`
+          echo $actions_user_id
+          echo "uid=$actions_user_id" >> $GITHUB_OUTPUT
 
       - name: Checkout the repo
         uses: actions/checkout@v2
@@ -42,6 +49,11 @@ jobs:
         run: |
           ./build_html.sh
 
+      - name: Reset ownership of workspace after build
+        uses: peter-murray/reset-workspace-ownership-action@v1
+        with:
+          user_id: ${{ steps.get_uid.outputs.uid }}
+
        # Push the book's HTML to github-pages
       - name: GitHub Pages action
         uses: peaceiris/[email protected]
@@ -52,11 +64,34 @@ jobs:
           destination_dir: pull${{ github.event.number }}
           # force_orphan: true # once peaceiris updates to v4, change this to true and keep_files: true for the PR / main branch deploy previews
 
+      - name: Checkout the gh-pages branch
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: '0'
+          ref: 'gh-pages'
+
+      - name: Run website diff
+        run: |
+          rustup update
+          pip install --upgrade pip
+          pip install website_diff
+          website_diff --old dev --new pull${{ github.event.number }} --diff diff${{ github.event.number }}
+
+      - name: GitHub Pages action to push diff
+        uses: peaceiris/[email protected]
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: diff${{ github.event.number }}
+          keep_files: true
+          destination_dir: diff${{ github.event.number }}
+          # force_orphan: true # once peaceiris updates to v4, change this to true and keep_files: true for the PR / main branch deploy previews
+
       - name: Post URLS to PR thread
         uses: mshick/[email protected]
         with:
           message: |
               Hello! I've built a preview of your PR so that you can compare it to the current `main` branch.
               * PR deploy preview available [here](https://datasciencebook.ca/pull${{ github.event.number }}/index.html)
+              * PR diff with `main` available [here](https://datasciencebook.ca/diff${{ github.event.number }}/index.html)
               * Current `main` deploy preview available [here](https://datasciencebook.ca/dev/index.html)
               * Public production build available [here](https://datasciencebook.ca)