Necessary expenses shall be refunded to every possessor; but only the possessor in good faith may retain the thing until he has been reimbursed therefor.
Useful expenses shall be refunded only to the possessor in good faith with the same right of retention, the person who has defeated him in the possession having the option of refunding the amount of the expenses or of paying the increase in value which the thing may have acquired by reason thereof. (453a)