instance method move

# File activerecord/lib/active_record/migration.rb, line 1394
      def move(direction, steps)
        migrator = Migrator.new(direction, migrations, schema_migration, internal_metadata)

        if current_version != 0 && !migrator.current_migration
          raise UnknownMigrationVersionError.new(current_version)
        end

        start_index =
          if current_version == 0
            0
          else
            migrator.migrations.index(migrator.current_migration)
          end

        finish = migrator.migrations[start_index + steps]
        version = finish ? finish.version : 0
        public_send(direction, version)
      end