Ensure that old API v1 generates still the same output

lib/ci/api/entities.rb

@@ -45,7 +45,25 @@ module Ci
         expose :artifacts_expire_at, if: ->(build, _) { build.artifacts? }
 
         expose :options do |model|
-          model.options
+          options = model.options
+
+          # This part ensures that output of old API is still the same after adding support
+          # for extended docker configuration options, used by new API
+          #
+          # I'm leaving this here, not in the model, because it should be removed at the same time
+          # when old API will be removed (planned for August 2017).
+          options[:image] = options[:image][:name] if options[:image].present? && options[:image].is_a?(Hash)
+          if options[:services].present?
+            options[:services].map! do |service|
+              if service.is_a?(Hash)
+                service[:name]
+              else
+                service
+              end
+            end
+          end
+
+          options
         end
 
         expose :timeout do |model|

spec/requests/ci/api/builds_spec.rb

@@ -137,6 +137,18 @@ describe Ci::API::Builds do
             end
           end
         end
+
+        context 'when docker configuration options are used' do
+          let!(:build) { create(:ci_build, :extended_options, pipeline: pipeline, name: 'spinach', stage: 'test', stage_idx: 0) }
+
+          it 'starts a build' do
+            register_builds info: { platform: :darwin }
+
+            expect(response).to have_http_status(201)
+            expect(json_response['options']['image']).to eq('ruby:2.1')
+            expect(json_response['options']['services']).to eq(['postgres', 'docker:dind'])
+          end
+        end
       end
 
       context 'when builds are finished' do