specify user before merging

.gitlab-ci.yml

@@ -83,5 +83,5 @@ merge into local:
     - master@solidstate/lectures
   script:
     - git checkout local
-    - git merge master
+    - git diff-index --quiet master || git -c "user.name=$GITLAB_USER_NAME" -c "user.email=$GITLAB_USER_EMAIL" merge master
     - "git push https://$GITLAB_PUSH_KEY@gitlab.kwant-project.org/solidstate/lectures.git local"