When editing a file named foo, Emacs will leave behind a foo~ backup file; or, if you’ve thought better of the edit and left without saving the buffer, you get #foo#.
Sometimes these files are nice to have! Most of the time they’re just annoying, so this tool recursively cleans them out of a directory.
Oh, this tool special-cases the .git directory, since I never want that cleaned up, but it does recurse into other hidden directories. Also if you have a loop caused by symbolic links it’ll keep chasing its tail until it blows the stack, so don’t do that.