The pleadings in a court of a magistrate may be amended at any time before or during the trial or upon appeal when by such amendment substantial justice will be promoted. If the amendment be made after the joining of the issue and it be made to appear to the satisfaction of the court, by oath, that an adjournment is necessary to the adverse party, in consequence of such amendment, an adjournment shall be granted. The court may also, in its discretion, require as a condition of an amendment the payment of costs to the adverse party.