Commit hash does not use same auto_now_add time

[jbinvnt]

The expected commit hash based on information stored in the database record does not match what is actually stored. This is likely because Django's auto_now_add appears to be calculated at a different time than the result of timezone.now() inside the save method. We need a way to get the value of auto_now_add inside save(), but the value of that field is None at that time.