fix a typo

* doc/tar.texi (Incremental Dumps): Add missing --file to the
'--list' example.

THANKS

@@ -140,6 +140,7 @@ Demizu Noritoshi	nori-d@is.aist-nara.ac.jp
 Denis Excoffier         denis.excoffier@free.fr
 Denis Fortin		fortin@acm.org
 Dennis Pixton		dennis@math.binghamton.edu
+Derek Terveer           dt@hawkmoon.mn.org
 Dick Streefland		dicks@tasking.nl
 Dietmar Braun		dietmar@highway.bertelsmann.de
 Dimitri Bougoulias	opus@hol.gr

doc/tar.texi

@@ -6645,7 +6645,7 @@ especially, the binary output it produced were considered inconvenient
 and were changed in version 1.16.}:
 
 @smallexample
-@kbd{tar --list --incremental --verbose --verbose archive.tar}
+@kbd{tar --list --incremental --verbose --verbose --file archive.tar}
 @end smallexample
 
 This command will print, for each directory in the archive, the list