Fetch PRs from upstream

.gitlab-ci.yml

@@ -56,6 +56,7 @@ setup_environment:
       git config user.name "${GIT_AUTHOR_NAME}";
       git config user.email "${GIT_AUTHOR_EMAIL}";
       git fetch upstream;
+      git fetch upstream '+refs/pull/*/head:refs/remotes/upstream/pr/*';
       git checkout -b integration;
       git merge upstream/uab-dev;
       cd ..;