anchor.diff:    lttngTools = lttng-tools;  # added 2014-07-31
     lttngUst = lttng-ust;  # added 2014-07-31
     jquery_ui = jquery-ui;  # added 2014-09-07
  -  youtubeDL = youtube-dl;  # added 2014-10-26
  -  youtube-dl = pythonPackages.youtube-dl; # added 2015-06-07
     rdiff_backup = rdiff-backup;  # added 2014-11-23
     htmlTidy = html-tidy;  # added 2014-12-06
     libtidy = html-tidy;  # added 2014-12-21
  
positive.code: 
    mg = callPackage ../applications/editors/mg { };
  
  
    # Attributes for backward compatibility.
    adobeReader = adobe-reader;
    arduino_core = arduino-core;  # added 2015-02-04
    asciidocFull = asciidoc-full;  # added 2014-06-22
  
negative.code:   sqliteInteractive = sqlite-interactive;  # added 2014-12-06
    nfsUtils = nfs-utils;  # added 2014-12-06
    buildbotSlave = buildbot-slave;  # added 2014-12-09
    rssglx = rss-glx; #added 2015-03-25
  
  }
    ### Other attribute aliases for backward compatibility.
    // lib.mapAttrs
        (name: builtins.trace "Warning: using a deprecated attribute '${name}'.")
  { # warnings since 2015-09
    youtubeDL = youtube-dl;  # added 2014-10-26
    youtube-dl = pythonPackages.youtube-dl; # added 2015-06-07
    cool-old-term = cool-retro-term; # added 2015-01-31
  
    haskell-ng = haskell;                 # 2015-04-19
    haskellngPackages = haskellPackages;  # 2015-04-19
    inherit (haskell.compiler) jhc uhc;   # 2015-05-15
  