/rotate (like tp, but doesn't interrupt motion or cancel entity riding)

Similar to /tp but the <x> <y> <z> arguments are gone.

Why is this useful? Commands like /tp <entity> ~ ~ ~ <yaw> <pitch> interrupts motion and ejects the entity from whatever it's currently riding, and this would get around those problems. This could be used to change a player's face direction while riding a horse, minecart, boat, etc.

This would also make custom entity motion easier to manage (no need for an extra entity to act as a "model" that is repeatedly teleported to the real one if you want control over rotation)