tar: fix bug with -C and extracting directories

Problem reported by Denis Excoffier in
<http://lists.gnu.org/archive/html/bug-tar/2010-10/msg00034.html>.

* src/extract.c (extract_dir): Use mkdirat, not mkdir.
* tests/extrac16.at: New file, to test for this bug.
* tests/Makefile.am (TESTSUITE_AT): Add it.
* tests/testsuite.at: Include it.

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src/extract.c

@@ -777,7 +777,7 @@ extract_dir (char *file_name, int typeflag)
 
   for (;;)
     {
-      status = mkdir (file_name, mode);
+      status = mkdirat (chdir_fd, file_name, mode);
       if (status == 0)
 	{
 	  current_mode = mode & ~ current_umask;

tests/Makefile.am

@@ -82,6 +82,7 @@ TESTSUITE_AT = \
  extrac13.at\
  extrac14.at\
  extrac15.at\
+ extrac16.at\
  filerem01.at\
  filerem02.at\
  gzip.at\

tests/extrac16.at

@@ -0,0 +1,36 @@
+# Process this file with autom4te to create testsuite. -*- Autotest -*-
+
+# Test suite for GNU tar.
+# Copyright (C) 2010 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
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+
+# This program 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/>.
+
+# written by Paul Eggert from a bug report by Denis Excoffier
+# <http://lists.gnu.org/archive/html/bug-tar/2010-10/msg00034.html>
+
+# Check extraction of empty directory with -C.
+
+AT_SETUP([extract empty directory with -C])
+AT_KEYWORDS([extract extrac16])
+
+AT_TAR_CHECK([
+mkdir src src/a src/a/b dest
+touch src/a/c
+
+tar -cf archive.tar -C src a &&
+tar -xf archive.tar -C dest
+],
+[0],[],[],[],[],[gnu])
+
+AT_CLEANUP

tests/testsuite.at

@@ -154,6 +154,7 @@ m4_include([extrac12.at])
 m4_include([extrac13.at])
 m4_include([extrac14.at])
 m4_include([extrac15.at])
+m4_include([extrac16.at])
 
 m4_include([label01.at])
 m4_include([label02.at])