anchor.diff:  let
     cfg = config.services.tarsnap;
   
  -  configFile = name: cfg: ''
  -    cachedir ${config.services.tarsnap.cachedir}/${name}
  +  configFile = cfg: ''
  +    cachedir ${config.services.tarsnap.cachedir}
       keyfile  ${config.services.tarsnap.keyfile}
       ${optionalString cfg.nodump "nodump"}
       ${optionalString cfg.printStats "print-stats"}
  
positive.code:           will refuse to run until you manually rebuild the cache with
            <command>tarsnap --fsck</command>.
  
            Note that each individual archive (specified below) has its own cache
            directory specified under <literal>cachedir</literal>; this is because
            tarsnap locks the cache during backups, meaning multiple services
            archives cannot be backed up concurrently or overlap with a shared
            cache.
  
            Set to <literal>null</literal> to disable caching.
          '';
        };
  
negative.code:         mkdir -p -m 0700 ${cfg.cachedir}
          chown root:root ${cfg.cachedir}
          chmod 0700 ${cfg.cachedir}
          DIRS=`cat /etc/tarsnap/$1.dirs`
          exec tarsnap --configfile /etc/tarsnap/$1.conf -c -f $1-$(date +"%Y%m%d%H%M%S") $DIRS
        '';
  