Function path_sort_key 

pub fn path_sort_key(path: &Path) -> String

The row sort key: byte-wise ascending on the /-joined UTF-8 path, not Path::cmp, which orders component-wise and disagrees with it (a.jpg vs a/b.jpg: joined, . sorts before /; component-wise, the bare a is a prefix of a.jpg and so sorts first). The rows end up serialized as those joined strings, so the joined order is the one a reader sees.