[skip ci] ci: Add workflow to serve documentation preview in PRs from…

… fork

.github/workflows/pr-serve-documentation-preview.yml

@@ -0,0 +1,71 @@
+name: serve documentation preview in PR
+
+on:
+  workflow_run:
+    workflows: [sphinx]
+    types: [completed]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions: {}
+
+jobs:
+  acquire-pr-context:
+    if: ${{ github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.conclusion == 'success' }}
+    runs-on: ubuntu-latest
+    outputs:
+      PR_NUMBER: ${{ steps.acquire-pr-context.outputs.number }}
+      PR_HEADSHA: ${{ steps.acquire-pr-context.outputs.headsha }}
+    permissions:
+      contents: read
+    steps:
+      - id: acquire-pr-context
+        run: gh pr view --repo "${REPOSITORY}" "${BRANCH}" --json 'number,headRefOid' --jq '"number=\(.number)\nheadsha=\(.headRefOid)"' >> "${GITHUB_OUTPUT}"
+        env:
+          GH_TOKEN: ${{ github.token }}
+          REPOSITORY: ${{ github.repository }}
+          BRANCH: |-
+            ${{
+              (github.event.workflow_run.head_repository.fork == true)
+              && format('{0}:{1}', github.event.workflow_run.head_repository.owner.login, github.event.workflow_run.head_branch)
+              || github.event.workflow_run.head_branch
+            }}
+
+  serve-documentation-preview:
+    if: ${{ github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.conclusion == 'success' }}
+    runs-on: ubuntu-latest
+    needs: [acquire-pr-context]
+    permissions:
+      actions: read
+      contents: read
+      pull-requests: write
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Download HTML artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: sphinx-html-artifact
+          path: html/
+          github-token: ${{ github.token }}
+          run-id: ${{ github.event.workflow_run.id }}
+
+      - name: Serve documentation preview
+        uses: ./.github/actions/sphinx/deploy
+        with:
+          CONFIGURATION: ${{ secrets.RCLONE_CONFIG_DOC_PREVIEW }}
+          BUCKET: ${{ vars.DOCUMENTATION_PREVIEW_BUCKET }}
+          SOURCE: html/
+          DESTINATION: ${{ needs.acquire-pr-context.outputs.PR_NUMBER }}/
+
+      - name: Comment with documentation preview link
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          number: ${{ needs.acquire-pr-context.outputs.PR_NUMBER }}
+          header: documentation-preview
+          message: >-
+            [Documentation preview](${{ vars.DOCUMENTATION_PREVIEW_URL }}/${{ needs.acquire-pr-context.outputs.PR_NUMBER }})
+            @ ${{ needs.acquire-pr-context.outputs.PR_HEADSHA }}