Function only_paths_in_parent_directory 

pub fn only_paths_in_parent_directory<'p, I, P>(
    paths: I,
) -> Option<&'p Utf8Path>
where
    I: IntoIterator<Item = &'p P> + Debug,
    P: AsRef<Utf8Path> + 'p + ?Sized,

Check if a set of paths all have the same parent directory and they are the only paths in that directory (other than dotfiles).