$ grep complete mkfs.bfs complete -F _bfs_module bfs So the file supposedly defines completion for 'mkfs.bfs' but instead attaches it to 'bfs', and there's no such executable in util-linux. I suppose that was supposed to be 'complete -F _bfs_module mkfs.bfs'.
sent patch upstream. not really a critical issue, so don't plan on patching in the tree.