This allows the repositories to be selected in the UI, if we are unsure whether the user has permission. Since gitlab will do the check anyway, this is safe, although not a great user experience if they chose an invalid repository, but we can't really do much about that.
users can only specify the folder and the
dockerfile must be names "Dockerfile" this allows
users to specify the file and it can be called
"Dockerfile" or <some name>.Dockerfile
