add branch_name method

Gemfile.lock

@@ -388,6 +388,3 @@ DEPENDENCIES
   travis-yaml!
   unicorn
   yard-sinatra!
-
-BUNDLED WITH
-   1.11.2

lib/travis/api/v3/models/request.rb

@@ -6,5 +6,12 @@ module Travis::API::V3
     has_many   :builds
     serialize  :config
     serialize  :payload
+
+    # has_one :branch_name,
+    #   primary_key: [:id,  :branch_name]
+
+    def branch_name
+      read_attribute(:branch_name)
+    end
   end
 end