Add a gitlab.yml conversion support script

CHANGELOG

@@ -2,6 +2,7 @@
 - Make SSH port in clone URLs configurable (Julien Pivotto)
 - Fix default Postgres port for non-packaged DBMS (Drew Blessing)
 - Add migration instructions coming from an existing GitLab installation (Goni Zahavy)
+- Add a gitlab.yml conversion support script
 6.8.1
 - Use gitlab-rails 6.8.1

support/gitlab_yml_converter.rb

+# This script translates settings from a gitlab.yml file to the format of
+# omnibus-gitlab's /etc/gitlab/gitlab.rb file.
+#
+# The output is NOT a valid gitlab.rb file! The purpose of this script is only
+# to reduce copy and paste work.
+#
+# Usage: ruby gitlab_yml_converter.rb /path/to/gitlab.yml
+
+require 'yaml'
+
+module GitlabYamlConverter
+  class Flattener
+    def initialize(separator='_')
+      @separator = separator
+    end
+
+    def flatten(hash, prefix=nil)
+      Enumerator.new do |yielder|
+        hash.each do |key, value|
+          raise "Bad key: #{key.inspect}" unless key.is_a?(String)
+          key = [prefix, key].join(@separator) if prefix
+
+          if value.is_a?(Hash)
+            flatten(value, key).each do |nested_key_value|
+              yielder.yield nested_key_value
+            end
+          else
+            yielder.yield [key, value]
+          end
+        end
+      end
+    end
+  end
+
+  def self.convert(gitlab_yml)
+    Flattener.new.flatten(gitlab_yml['production']).each do |key, value|
+      puts "gitlab_rails['#{key}'] = #{value.inspect}"
+    end
+  end
+end
+
+if $0 == __FILE__
+  GitlabYamlConverter.convert(YAML.load(ARGF.read))
+end