anchor.diff:            };
   
             archiveBaseName = mkOption {
  -            type = types.strMatching "[^/{}]+";
  +            type = types.nullOr (types.strMatching "[^/{}]+");
               default = "${globalConfig.networking.hostName}-${name}";
               defaultText = literalExpression ''"''${config.networking.hostName}-<name>"'';
               description = ''
  
positive.code:     }
      trap 'on_exit' INT TERM QUIT EXIT
  
      archiveName="${cfg.archiveBaseName}-$(date ${cfg.dateFormat})"
      archiveSuffix="${optionalString cfg.appendFailedSuffix ".failed"}"
      ${cfg.preHook}
    '' + optionalString cfg.doInit ''
  
negative.code:               determined by <option>dateFormat</option>, will be appended. The full
                name can be modified at runtime (<literal>$archiveName</literal>).
                Placeholders like <literal>{hostname}</literal> must not be used.
                Use <literal>null</literal> for no base name.
              '';
            };
  
  