It turns out that the code to track redirects (playlists and
directories) never worked correctly, only the last redirect is
remembered and num_redirects is never greater than 1.
You can see this by doing quit-watch-later with the old watch later
system, before dbf244fd2f, on a m3u playlist of files and a m3u playlist
of directories. Only in the first case a redirect entry for the m3u file
is created, because in the second case the m3u redirect is replaced by
the directory one.
If you did mpv --directory-mode=lazy /foo it did create redirect entries
for all subdirectories e.g. /foo/bar, /foo/bar/baz, /foo/bar/baz/qux,
this made it seem like it worked correctly, but actually
/foo/bar/bar/qux was the only redirect entry and thus it was considered
as the first redirect, and mpv created redirect entries for each segment
of the first redirect only.
In the previous commit dbf244fd2f, rather than figuring out how to fix
the code to track redirects, and since creating redirect entries for
multiple redirects is overkill, I just used the new playlist-path
property which does the same thing but only for the last redirect.
By replacing the only other use of the old redirect code with
playlist-path, we can remove it.
e1f9444d4d