If I right click a torrent and "Move data", and previous and selected target directory are on the same file system, the files remain sparse. If on the other hand previous and selected target directory are on different file systems, they are expanded. I would like them to remain sparse even in the latter case.

Assuming that the actual move happens in MoveDataFilesJob, the culprit seems to be the calls to KIO::file_move. I can imagine two possible "solutions":

• If a simple rename fails, copy the file with ktorrent's knowledge of which blocks actually need to be copied.
• Pimp up KIO so that it recognizes sparse files similar to GNU's cp.

I have no plan of adding some special sparse file copy function to ktorrent. Do not want to clutter up ktorrent with the low level details of file copying. It will have to be added to KIO.