If you think of it not as a "rename" (which would belong in the edge object if it existed) but rather as a "note: the file A in this tree was known as B in the

If you think of it not as a "rename" (which would belong in the edge object if it existed) but rather as a "note: the file A in this tree was known as B in the parent tree" it would make perfect sense to store it in the child commit.