migrate

# File activerecord/lib/active_record/migration.rb, line 1058
    def migrate(target_version = nil, &block)
      case
      when target_version.nil?
        up(target_version, &block)
      when current_version == 0 && target_version == 0
        []
      when current_version > target_version
        down(target_version, &block)
      else
        up(target_version, &block)
      end
    end