anchor.diff:  { stdenv, lib, fetchFromGitHub, writeScript, glibcLocales, diffPlugins, substituteAll
   , pythonPackages, imagemagick, gobject-introspection, gst_all_1
  -, runtimeShell
  -, unstableGitUpdater
  +, runtimeShell, unstableGitUpdater
   
   # external plugins package set
   , beetsExternalPlugins
   
  -, enableAbsubmit         ? lib.elem stdenv.hostPlatform.system essentia-extractor.meta.platforms, essentia-extractor ? null
  +, enableAbsubmit         ? lib.elem stdenv.hostPlatform.system essentia-extractor.meta.platforms, essentia-extractor
   , enableAcousticbrainz   ? true
   , enableAcoustid         ? true
  -, enableBadfiles         ? true, flac ? null, mp3val ? null
  +, enableBadfiles         ? true, flac, mp3val
   , enableBeatport         ? true
   , enableBpsync           ? true
  -, enableConvert          ? true, ffmpeg ? null
  +, enableConvert          ? true, ffmpeg
   , enableDeezer           ? true
   , enableDiscogs          ? true
   , enableEmbyupdate       ? true
   , enableFetchart         ? true
   , enableGmusic           ? true
  -, enableKeyfinder        ? true, keyfinder-cli ? null
  +, enableKeyfinder        ? true, keyfinder-cli
   , enableKodiupdate       ? true
   , enableLastfm           ? true
   , enableLoadext          ? true
  
positive.code:     EDITOR="${writeScript "beetconfig.sh" ''
        #!${runtimeShell}
        cat > "$1" <<CFG
        plugins: ${concatStringsSep " " allEnabledPlugins}
        CFG
      ''}" HOME="$tmphome" "$out/bin/beet" config -e
      EDITOR=true HOME="$tmphome" "$out/bin/beet" config -e
  
negative.code:     # bs1770gain, and set the absolute path there, to avoid impurities.
      ++ lib.optional enableReplaygain (substituteAll {
        src = ./replaygain-default-ffmpeg.patch;
        ffmpeg = lib.getBin ffmpeg;
      })
      # Put absolute Nix paths in place
      ++ lib.optional enableConvert (substituteAll {
        src = ./convert-plugin-ffmpeg-path.patch;
        ffmpeg = lib.getBin ffmpeg;
      })
      ++ lib.optional enableBadfiles (substituteAll {
        src = ./badfiles-plugin-nix-paths.patch;
  