Run build with external gitlab-ci.yml

Feature request:

Often many commits are wasted while trying to write a functional gitlab-ci.yml. It would be nice if there is the possibility to run builds with an external testing gitlab-ci.yml, which is uploaded to gitlab web interface and not checked in into the git repository. This can be an extension to gitlab-ci.yml lint. It'd be nice if one could select the repo, branch and commit to test the yml with...