[emms-help] emms-cache-set-from-mpd-all mixes info fields from mpd tag_cache

[Julien Cubizolles]

I noticed a while ago that sometimes emms-cache-set-from-mpd-all creates
wrong entries in the emms cache from tag_cache, namely for some songs,
the info-title and/or info-artist aren't set and there's a shift in this
field for all the following songs.

For instance, if I have

song 0 - artist 0
song 1 - artist 1
song 2 - artist 2
song 3 - artist 3

in MPD tag_cache

I will sometimes have (they are included in reverse ordre) in emms cache:

song 3 - artist 2
song 2 - artist 1
song 1 - no artist
song 0 - artist 0

I provided some more detailed examples in
http://permalink.gmane.org/gmane.emacs.emms.user/1768.

I'm up to date with the git repo of emms but emms-player-mpd.el (where
emms-cache-set-from-mpd-all is defined) hasn't been touched in a while.

This bug is very annoying since a problem in one file messes up the
whole database. Emms is a really nice tool, and I can create the
playlist with emms-add-playlist-directory but it's much slower of than
using the one mpd maintains independently.

Julien.