Currently we use file:// where I believe MPD uses paths that are relative to the configured folder. We should probably fix this so we can use mopidy tag caches with MPD and vica versa. For your average end user this is not likely to make any difference, but for development and comparing the protocol output this matters.
The alternative would of course be to have the debug proxy be aware of this difference and apply some magic regexp to mitigate false positives for this type of issue.
Furthermore I believe we also return file:// in most protocol replies where MPD would just use the relative one.
For the longer term future of the locale library using woosh or sqlite lite would be better than tag caches.
Closing since we will be aiming for #291 as better use of our time.