Attach an artifact containing the pr number to the build

.github/workflows/ci-actions-incremental.yml

@@ -40,6 +40,25 @@ env:
   DB_PASSWORD: hibernate_orm_test
   DB_NAME: hibernate_orm_test
 jobs:
+  # This is a hack to work around a GitHub API limitation:
+  # when the PR is coming from another fork, the pull_requests field of the
+  # workflow_run payload is empty.
+  # For more details, see
+  # https://github.community/t/pull-request-attribute-empty-in-workflow-run-event-object-for-pr-from-forked-repo/154682
+  attach-pr-number:
+    runs-on: ubuntu-latest
+    name: Attach pull request number
+    if: github.event_name == 'pull_request'
+    steps:
+      - name: Create file
+        shell: bash
+        run: |
+          echo -n ${{ github.event.number }} > pull-request-number
+      - name: Upload pull request number
+        uses: actions/upload-artifact@v2
+        with:
+          name: pull-request-number-${{ github.event.number }}
+          path: pull-request-number
   ci-sanity-check:
     name: "CI Sanity Check"
     runs-on: ubuntu-latest