Remove requirement of `config_file` by generating `external_url` from `dns_name`
If we use a method similar to that for runner_host
, we can remove the need of config_file
altogether, as we'll then have no hard requirement for any part of gitlab.rb
that has not already been provided via arguments.
This will remove additional steps from the basic deployments of GitLab, but allow advanced behaviors for those interested in further controlling the deployment.