default gitlab.relative_url_root to ENV['RAILS_RELATIVE_URL_ROOT']
Settings.gitlab['host'] ||= 'localhost'
Settings.gitlab['https'] = false if Settings.gitlab['https'].nil?
Settings.gitlab['port'] ||= Settings.gitlab.https ? 443 : 80
-Settings.gitlab['relative_url_root'] ||= ''
+Settings.gitlab['relative_url_root'] ||= ENV['RAILS_RELATIVE_URL_ROOT'] || ''
Settings.gitlab['protocol'] ||= Settings.gitlab.https ? "https" : "http"
Settings.gitlab['email_from'] ||= "gitlab@#{Settings.gitlab.host}"
Settings.gitlab['support_email'] ||= Settings.gitlab.email_from