https://bugs.winehq.org/show_bug.cgi?id=45935
--- Comment #10 from Joshua joshudson@gmail.com ---
It's already the fallback for moving files across filesystems (i.e. rename() returns EXDEV).
The particular caller I'm using is guaranteed to never try to span filesystems due to source and target being in the same directory. I suppose I could have said MoveFileEx(sourcefile, taragetfle, 0); which must fail on EXDEV.