bash-my-github and bash-my-spotify are two things I've made a start on but are not public yet. They've been on the backburner for a while due to competing priorities.

I was able to write a simple command that returned all songs a friend and I had in common in our public playlists.

I forget the exact syntax but it was something roughly along the lines of:

  $ sort <(
      user-playlists alice | playlist-tracks 
      user-playlists bob | playlist-tracks
    ) | uniq --repeated