anchor.diff:          visible = false;
         });
         config.warnings = optional (getAttrFromPath option config != null)
  -        "The option ${showOption option} defined in your configuration no longer has any effect; please remove it.";
  +        "The option `${showOption option}' defined in your configuration no longer has any effect; please remove it.";
       };
   
   in zipModules ([]
  
positive.code:     name = "Alias";
      use = id;
      define = id;
    };
  
    obsolete = from: to: rename {
      inherit from to;
      name = "Obsolete name";
      use = x: builtins.trace "Obsolete option ${showOption from} is used instead of ${showOption to}." x;
      define = x: builtins.trace "Obsolete option ${showOption from} is defined instead of ${showOption to}." x;
    };
  
    deprecated = from: to: rename {
      inherit from to;
      name = "Deprecated name";
      use = x: abort "Deprecated option ${showOption from} is used instead of ${showOption to}.";
      define = x: abort "Deprecated option ${showOption from} is defined instead of ${showOption to}.";
    };
  
    showOption = name: "`${concatStringsSep "." name}'";
  
    zipModules = list:
      zipAttrsWith (n: v:
  
negative.code:       else head v
      ) list;
  
    rename = { from, to, name, use, define, visible ? false }:
      let
        setTo = setAttrByPath to;
        setFrom = setAttrByPath from;
        toOf = attrByPath to
          (abort "Renaming error: option `${showOption to}' does not exists.");
        fromOf = attrByPath from
          (abort "Internal error: option `${showOption from}' should be declared.");
      in
        [ { options = setFrom (mkOption {
              description = "${name} of <option>${showOption to}</option>.";
              apply = x: use (toOf config);
              inherit visible;
            });
          }
          { options = setTo (mkOption {
  