join_table.rb

module ActiveRecord
  class Migration
    module JoinTable #:nodoc:
      private

      def find_join_table_name(table_1, table_2, options = {})
        options.delete(:table_name) || join_table_name(table_1, table_2)
      end

      def join_table_name(table_1, table_2)
        [table_1, table_2].sort.join("_").to_sym
      end
    end
  end
end