The pleadings may be amended at any time before the trial, or during the trial, or upon appeal, to supply any deficiency or omissions in the allegations or denials, necessary to support the action or defense, when by such amendment substantial justice will be promoted. If the amendment be made after the issue, and it be made to appear to the satisfaction of the court that a continuance is necessary to the adverse party in consequence of such amendment, a continuance 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.