Checkout the latest version of the pull-request

Also trigger because action has been updated

.github/workflows/gitlab_ci.yml

@@ -68,7 +68,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
         with:
-          ref: "${{ github.event.pull_request.merge_commit_sha }}"
+          ref: "${{ github.event.pull_request.head.sha }}"
           persist-credentials: false
       - name: Mirror and wait for Gitlab-CI
         uses: jakob-fritz/github2lab_action@Iss35_mirror_pr