ci: skip GH Pages publish from fork PRs

Author: cwillisf

.github/workflows/ci.yml

@@ -90,7 +90,9 @@ jobs:
   preview:
     runs-on: ubuntu-latest
     needs: build
-    if: ${{ needs.build.outputs.any-workspace == 'true' }}
+    # Skip publishing to GH Pages if nothing changed or if this PR is coming from a fork
+    # See also https://github.com/orgs/community/discussions/26829#discussioncomment-3253575
+    if: ${{ (needs.build.outputs.any-workspace == 'true') && ( github.event.pull_request.head.repo.full_name == github.repository ) }}
     name: Publish preview playgrounds to GH Pages
     steps:
       - name: Determine GitHub Pages directory name