Function split_path 

pub fn split_path(path: &str) -> Option<(String, String)>

Splits a path into (directory, filename).

Returns None if the path is empty or contains only separators.

Examples

assert_eq!(split_path("dir/file.txt"), Some(("dir".into(), "file.txt".into())));
assert_eq!(split_path("file.txt"), Some(("".into(), "file.txt".into())));
assert_eq!(split_path("/a/b/c.txt"), Some(("a/b".into(), "c.txt".into())));
assert_eq!(split_path(""), None);
assert_eq!(split_path("/"), None);