If I wanted to keep a copy on my desktop of the photos on my phone, and organize those photos into several folders, how would I avoid re-copying photos I've already copied?
If I drop all my photos into a single folder, this is trivial: if there is already a file with the same name in the destination folder, then don't copy that one.
But if I drop the photos into multiple folders, that simple check won't work—the photo might have already been copied into a different folder!
What do?