        ⇒ base → Maybe mod → FilePath → IO ([AssocFile base],[AssocFile mod])
getFiles base (Just mod) subPath = do
  modFiles ← getDirectoryFiles mod ("geheimnisnacht" <> "/"<>subPath<>"/")
  baseFiles ← filter (not . flip elem modFiles) <$> getDirectoryFiles base ("/"<>subPath<>"/")
  return (map (getFile base) baseFiles,map (getFile mod) modFiles)
getFiles base Nothing subPath = do
  baseFiles ← getDirectoryFiles base ("/"<>subPath<>"/")
  r
getFiles :: (FileCollection base, FileCollection mod)
            ⇒ base → Maybe mod → FilePath → IO ([AssocFile base],[AssocFile mod])
getFiles base (Just mod) subPath = do
  modFiles ← getDirectoryFiles mod ("geheimnisnacht" <> "/"<>subPath<>"/")
  baseFiles ← filter (not . flip elem modFiles) <$> getDirectoryFiles base ("/"<>subPath<>"/")
  return (map (getFile base) baseFiles,map (getFile mod) modFiles)
getFiles base (Just mod) subPath = do
  modFiles ← getDirectoryFiles mod ("geheimnisnacht" <> "/"<>subPath<>"/")
  baseFiles ← filter (not . flip elem modFiles) <$> getDirectoryFiles base ("/"<>subPath<>"/")
  return (map (getFile base) baseFiles,map (getFile mod) modFiles)