Add `cat-playlists`

Add a script to concatenate playlists from subdirectories.

diff --git a/audio/cat-playlists b/audio/cat-playlists
new file mode 100755 (executable)
index 0000000..cd18eac
--- /dev/null
+++ b/audio/cat-playlists
@@ -0,0 +1,7 @@
+#! /bin/sh
+set -e
+
+find . -mindepth 1 -type d -printf '"%P"\n' | sort | sed 's/`/\\`/' |
+xargs -I% -n1 sh -c \
+    'test -f "%"/PlayList.m3u && cat "%"/PlayList.m3u | sed -e "s\^\%/\\"' \
+> PlayList.m3u