How can I move a file to a new folder with a new name atomically?

[garyhooper]

I see no equivalent to FileManager's replaceItemAt (https://developer.apple.com/documentation/foundation/filemanager/2293212-replaceitemat). This is equivalent to linux mv dir1/old_name dir2/new_name.

Is this possible? If not, could it be added? The use case is downloading a file to a temporary folder with a unique name, and then moving it to its true home and name upon successful download.