The parser implemented in libmpdclient requires the first key-value pair
of the server response to be the file pair. This is due to the fact that
libmpdclient scan pairs sequentially and first attempts to extract the
file pair before parsing the currentsong response further. See:
5c751a761e/src/song.c (L559-L563)
Meta data encoded as pairs in the currentsong response will be ignored
if they are placed before the file pair in the response.
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