gitlab-ci/README: How not to run on forks (#6)

Add instructions on how to skip this action on forks or pull requests from forks due to missing secrets.

Signed-off-by: Nils Wistoff <[email protected]>

gitlab-ci/README.md

@@ -26,7 +26,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check Gitlab CI
-        uses: pulp-platform/pulp-actions/gitlab-ci@v1
+        uses: pulp-platform/pulp-actions/gitlab-ci@v2
+        # Skip on forks or pull requests from forks due to missing secrets.
+        if: github.repository == 'pulp-platform/cheshire' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository)
         with:
           domain: iis-git.ee.ethz.ch
           repo: github-mirror/cheshire