code: func newDeltaObjectToPack(base *ObjectToPack, original, delta plumbing.EncodedObject) *ObjectToPack {
  	return &ObjectToPack{
  		Object:   delta,
  		Base:     base,
  		Original: original,
  		Depth:    base.Depth + 1,
  	}
  }
docs: // newDeltaObjectToPack creates a correct ObjectToPack for a delta object, based on
  // his base (could be another delta), the delta target (in this case called original),
  // and the delta Object itself