Sec. 2. If a defendant appeals his conviction and is released on bail pending disposition of his appeal, when his conviction is affirmed, the clerk of the trial court, on receipt of the mandate from the appellate court, shall issue a commitment against the defendant. The officer executing the commitment shall endorse thereon the date he takes the defendant into custody and the defendant's sentence begins to run from the date endorsed on the commitment. The Texas Department of Criminal Justice shall admit the defendant named in the commitment on the basis of the commitment.