def versioned_columns
      case
        when vestal_versions_options[:only] then self.class.column_names & vestal_versions_options[:only]
        when vestal_versions_options[:except] then self.class.column_names - vestal_versions_options[:except]
        else self.class.column_names
      end - %w(created_at created_on updated_at updated_on)
    end
def versioned_columns
      case
        when vestal_versions_options[:only] then self.class.column_names & vestal_versions_options[:only]
        when vestal_versions_options[:except] then self.class.column_names - vestal_versions_options[:except]
        else self.class.column_names
      end - %w(created_at created_on updated_at updated_on)
    end
Returns an array of column names that should be included in the changes of created
 versions. If <tt>vestal_versions_options[:only]</tt> is specified, only those columns
 will be versioned. Otherwise, if <tt>vestal_versions_options[:except]</tt> is specified,
 all columns will be versioned other than those specified. Without either option, the
 default is to version all columns. At any rate, the four "automagic" timestamp columns
 maintained by Rails are never versioned.