Fix more -t/-x discrepancies

Problem reported by Guillermo de Angel in:
https://lists.gnu.org/r/bug-tar/2026-03/msg00007.html
* THANKS: Add him, and sort.
* src/extract.c (extract_dir, extract_file):
* src/incremen.c (purge_directory):
Do not call skip_member, as the caller now does that, and does it
more reliably.
* src/extract.c (extract_file):
Mark file as skipped when we’ve read it.
(extract_archive): Always call skip_member after extracting,
as it suppresses the skip as needed.
* src/incremen.c (try_purge_directory): Remove; no longer
needed.  Move internals to purge_directory.
* src/list.c (read_header): Do not treat LNKTYPE header as having
size zero, as it can be nonzero (e.g., ‘pax -o linkdata’).
Set info->skipped field according to how the header was read.
(member_is_dir): Remove; no longer needed.
(skim_member): Skip directory data too, unless it’s already been
skipped (i.e., read).
* tests/extrac32.at: New file.
* tests/Makefile.am (TESTSUITE_AT):
* tests/testsuite.at:
Add it.
* tests/skipdir.at (skip directory members):
Fix test to match the correct behavior.
This fixes a bug introduced in commit
b009124ffd
dated 2025-05-12 17:17:21 +0300.

tests/Makefile.am

@@ -141,6 +141,7 @@ TESTSUITE_AT = \
  extrac29.at\
  extrac30.at\
  extrac31.at\
+ extrac32.at\
  filerem01.at\
  filerem02.at\
  filerem03.at\

tests/extrac32.at

@@ -0,0 +1,47 @@
+# Check for file injection bug with symlinks. -*- Autotest -*-
+
+# Copyright 2026 Free Software Foundation, Inc.
+
+# This file is part of GNU tar.
+
+# GNU tar is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+
+# GNU tar is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Thanks to Guillermo de Angel for the bug report and test cases; see:
+# https://lists.gnu.org/r/bug-tar/2026-03/msg00007.html
+
+AT_SETUP([skip file injection])
+AT_KEYWORDS([injection])
+AT_DATA([archive.in],
+[/Td6WFoAAATm1rRGBMDbAYAcIQEcAAAAAAAAACYr+9LgDf8A010AMZhKvfVdtHe4Rxjj7M03ek97
+UgeKfJ0ORqYg0XDFntWxdTH4PYrTOo9CoqBrnTM2NcwFBrRVr7aFwdd56vddyAw2QGDjxgNexDU3
+ImTi/+z8ZOLMi/+AybdEpd5aA/M9Maa+8tQ84bySzSAwrmxMWJJ6W9IKvsqfiRa3TrD51v44PZU/
+KLVKpocS56n/O3g+b+hiZwaysR0eLO+tiU8FB/e3PEq3vTtDFVi/YfZMieBWSzomSX9eF13K1yPY
+UuWgp7VokXqduL0YGNVV40MTPG9oAAAApD6mpajengIAAfcBgBwAAOM4xw6xxGf7AgAAAAAEWVo=
+])
+AT_CHECK([base64 --help >/dev/null 2>&1 || AT_SKIP_TEST
+xz --help >/dev/null 2>&1 || AT_SKIP_TEST
+base64 -d < archive.in | xz -c -d > archive.tar
+])
+cp archive.tar /tmp
+AT_CHECK([tar tf archive.tar],
+[0],
+[carrier_entry
+marker.txt
+])
+AT_CHECK([tar xvf archive.tar],
+[0],
+[carrier_entry
+marker.txt
+])
+AT_CLEANUP

tests/skipdir.at

@@ -42,15 +42,11 @@ base64 -d < archive.in | xz -c -d > archive.tar
 AT_CHECK([tar tf archive.tar],
 [0],
 [owo1/
-owo2/
 ])
 AT_CHECK([tar vxf archive.tar],
 [0],
 [owo1/
-owo2/
 ])
 AT_CHECK([tar -xvf archive.tar --exclude owo1],
-[0],
-[owo2/
-])
+[0])
 AT_CLEANUP

tests/testsuite.at

@@ -358,6 +358,7 @@ m4_include([extrac28.at])
 m4_include([extrac29.at])
 m4_include([extrac30.at])
 m4_include([extrac31.at])
+m4_include([extrac32.at])
 
 m4_include([backup01.at])