playlist_song: fix absolute path support in playlists

Right now, a playlist with absolute pathnames can only add songs that
are in the same the directory of the playlist or under it.

If uri is an absolute pathname and base_uri is set,
playlist_check_translate_song() will check that base_uri is a prefix
of uri, excluding every other song in the music directory outside
base_uri.

I think in this case base_uri should be completely ignored (and made
NULL) and uri should just be checked against music root directory.

NEWS

@@ -15,6 +15,7 @@ ver 0.16.5 (2010/??/??)
   - the "seek" command works when MPD is stopped
   - restore song position from state file (bug fix)
   - fix crash that sometimes occurred when audio device fails on startup
+  - fix absolute path support in playlists
 * WIN32: close sockets properly
 * install systemd service file if systemd is available
 

src/playlist_song.c

@@ -114,9 +114,7 @@ playlist_check_translate_song(struct song *song, const char *base_uri)
 
 	if (g_path_is_absolute(uri)) {
 		/* XXX fs_charset vs utf8? */
-		char *prefix = base_uri != NULL
-			? map_uri_fs(base_uri)
-			: map_directory_fs(db_get_root());
+		char *prefix = map_directory_fs(db_get_root());
 
 		if (prefix == NULL || !g_str_has_prefix(uri, prefix) ||
 		    uri[strlen(prefix)] != '/') {
@@ -127,6 +125,7 @@ playlist_check_translate_song(struct song *song, const char *base_uri)
 			return NULL;
 		}
 
+		base_uri = NULL;
 		uri += strlen(prefix) + 1;
 		g_free(prefix);
 	}