Add CI config for mirror branch

.gitlab-ci.yml

@@ -69,3 +69,23 @@ gruppen:
     - ./flammenwehrfer.sh
   tags:
     - alive
+
+# mirror master branch to unprotected mirror branch to allow members with Developer role to trigger CI runs
+# (copied from https://forum.gitlab.com/t/is-it-possible-to-commit-artifacts-into-the-git/22218/7)
+mirror:
+  stage: run
+  only:
+    - master
+  before_script:
+    - 'which ssh-agent || ( apt-get update -qy && apt-get install openssh-client -qqy )'
+    - eval `ssh-agent -s`
+    - echo "$SSH_PRIVATE_KEY_MIRROR" | tr -d '\r' | ssh-add - > /dev/null # add ssh key
+    - mkdir -p ~/.ssh
+    - chmod 700 ~/.ssh
+    - echo "$SSH_PUBLIC_KEY_MIRROR" >> ~/.ssh/id_rsa.pub
+    - '[[ -f /.dockerenv ]] && echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config'
+  script:
+    - git remote rm origin && git remote add origin git@gitlab.com:$CI_PROJECT_PATH.git
+    - git fetch origin master
+    - git push origin refs/remotes/origin/master:refs/heads/mirror
+