anchor.diff:          (lib.splitString "\n" (builtins.readFile file));
         removeComments = lib.filter (line: !(lib.hasPrefix "#" line));
         relativePaths = removeComments lines;
  -      absolutePaths = builtins.map (path: builtins.toPath (root + "/" + path)) relativePaths;
  +      absolutePaths =
  +        builtins.map (path: builtins.toPath (root + "/" + path)) relativePaths;
       in
         absolutePaths;
   
  
positive.code:   #    lib.getVersion pkgs.youtube-dl         ==> "2016.01.01"
    getVersion = x: (builtins.parseDrvName (x.name or x)).version;
  
  
    # Extract name with version from URL. Ask for separator which is
    # supposed to start extension.
    nameFromURL = url: sep:
  
negative.code:       components = splitString "/" url;
        filename = lib.last components;
        name = builtins.head (splitString sep filename);
      in
      assert name !=  filename;
      name;
  
    # Create a fixed width string with additional prefix to match
    # required width.
  