avoid failure of txinfo18.test due to texi2dvi and my paranoia

[Jim Meyering]

Some versions of texi2dvi do this:

    tar cf - $xref_files_orig | (cd "$work_bak" && tar xf -)

but when the files it's trying to extract already exist,
and TAR_OPTIONS=--keep-old-files is set in the environment, it fails.
Since texi2dvi4.13, it does this:

    TAR_OPTIONS=; export TAR_OPTIONS
    tar cf - $xref_files_orig | (cd "$work_bak" && tar xf -)

In the mean time, with texi2dvi-4.12, automake's "make check" fails
for me, since I do set TAR_OPTIONS=--keep-old-files in my environment.
-----------

FAIL: txinfo18.test (exit: 2)

=============================

...
Output written on main.dvi (1 page, 236 bytes).
Transcript written on main.log.
tar: main.au: Cannot open: File exists
tar: main.cp: Cannot open: File exists
tar: main.pg: Cannot open: File exists
tar: main.sb: Cannot open: File exists
tar: Exiting with failure status due to previous errors
make[1]: *** [main.dvi] Error 2
make[1]: Leaving directory `/h/meyering/w/co/automake/tests/txinfo18.dir/txinfo1
8-1.0/_build'
make: *** [distcheck] Error 2
+ exit_status=2
+ cd /h/meyering/w/co/automake/tests
+ case $exit_status,$keep_testdirs in
+ test 0 '!=' 0
+ echo ': exit 2'
: exit 2
+ exit 2


I'm probably the only one to run "make check" with this
envvar setting, and on a system with the slightly-outdated texi2dvi.
In case you're interested, here's the patch I'm using:

>From d5fbc42aaaf7df619235c80e877c7431611d8be2 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Mon, 30 Mar 2009 08:17:48 +0200
Subject: [PATCH] avoid test failure due to paranoid TAR_OPTIONS envvar setting

* tests/txinfo18.test: Don't let a TAR_OPTIONS=--keep-old-files
envvar setting cause test failure.  texi2dvi v
---
 ChangeLog           |    6 ++++++
 tests/txinfo18.test |    4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index fe63988..103e763 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2009-03-30  Jim Meyering  <address@hidden>
+
+       avoid test failure due to paranoid TAR_OPTIONS envvar setting
+       * tests/txinfo18.test: Don't let a TAR_OPTIONS=--keep-old-files
+       envvar setting cause test failure.  texi2dvi v
+
 2009-03-29  Ralf Wildenhues  <address@hidden>

        * NEWS: Minor update.
diff --git a/tests/txinfo18.test b/tests/txinfo18.test
index f847b63..bc66918 100755
--- a/tests/txinfo18.test
+++ b/tests/txinfo18.test
@@ -1,5 +1,5 @@
 #! /bin/sh
-# Copyright (C) 2002, 2008  Free Software Foundation, Inc.
+# Copyright (C) 2002, 2008, 2009  Free Software Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -62,4 +62,4 @@ $AUTOMAKE --add-missing
 $AUTOCONF

 ./configure
-$MAKE distcheck
+TAR_OPTIONS= $MAKE distcheck
--
1.6.2.rc1.285.gc5f54