<> = *file ->                                    [] = file ->
  file.tmp-name = fs FS_TMP                        if (file.tmp-name && file-exists file.tmp-name) ->
_                                                    - fs FS_DELETE file.tmp-name
  file : file-in-queue                             ;
;                                                _
                                                   file : file-in-queue
                                                 ;
