title: Non-blocking worker - interrupt file copy
body: <p>I'm dealing with very large files, in excess of hundreds of GB in size. The User needs to be able to move these files between disks and is on a restricted system with no default file manager. It's possible for the User to realize they've made a mistake and cancel the operation, and as far as I can tell the User will have to wait for the current copy or rename operation to complete. This can leave them feeling frustrated as they wait potentially minutes, only to see that their many GB file still copied. In the case of Copy I could delete the second file, but in the case of rename, which I'm using to move files, I'd have to repeat the operation in reverse to undo it, and that's simply not acceptable.</p>
  
  <p>Is there some way to interrupt copy() and rename() that I'm not seeing in the documentation for QFile, or will I need to put together my own class to handle copy and rename?</p>