anchor.diff:      }
       trap 'on_exit' INT TERM QUIT EXIT
   
  -    archiveName="${cfg.archiveBaseName}-$(date ${cfg.dateFormat})"
  +    archiveName="${if cfg.archiveBaseName == null then "" else cfg.archiveBaseName + "-"}$(date ${cfg.dateFormat})"
       archiveSuffix="${optionalString cfg.appendFailedSuffix ".failed"}"
       ${cfg.preHook}
     '' + optionalString cfg.doInit ''
  
positive.code:           };
  
            prune.prefix = mkOption {
              type = types.str;
              description = ''
                Only consider archive names starting with this prefix for pruning.
                By default, only archives created by this job are considered.
                Use <literal>""</literal> to consider all archives.
              '';
              default = config.archiveBaseName;
              defaultText = literalExpression "archiveBaseName";
  
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.
              '';
            };
  
  