gistfile1.rb

    module VersionedExtensions
      
      def save_version?
        false
      end
      
      def set_version(v)
        self.version = v
        update_without_callbacks
      end
      
      def forcing_new_version
        def self.save_version? ; true ; end
        @saving_version = true
        self.class.transaction { yield }
      ensure
        def self.save_version? ; false ; end
        @saving_version = false
      end
      
      protected
      
      def set_new_version
        true
      end
      
    end
    
    module VersionedChildExtensions
      
      def make_new_version!(v)
        forcing_new_version do
          set_version(v)
          save_version
        end
      end
      
    end