I have a directory that contains many subdirectories. The subdirectories contain lots of types of files with different file extensions. I want to move (not copy) all the files of one type into a new directory. I need all these files to be in the same directory, i.e. it needs to be flat.
(My use case is that I want to move ebooks called *.epub from many directories into a single folder that an EPUB reader can find.)