In the following patches we will be adding more and more settings to
read from gitlab config, so structure of code which does this is better
prepared:

    - part that emits the settings (in Ruby) is now multiline
    - we prepare shortcuts c & s which are Gitlab.config and
      Gitlab.config.gitlab_shell
    - in the end there is "END" emitted, and the reader checks this to
      make sure generate and read parts stay in sync.

/cc @kazuhiko