sort: add a test case for the sort -u bug

* tests/Makefile.am (TESTS): Add misc/sort-unique.
* tests/misc/sort-unique: New file.

tests/Makefile.am

@@ -234,6 +234,7 @@ TESTS =						\
   misc/sort-merge-fdlimit			\
   misc/sort-month				\
   misc/sort-rand				\
+  misc/sort-unique				\
   misc/sort-version				\
   misc/split-a					\
   misc/split-fail				\

tests/misc/sort-unique

@@ -0,0 +1,46 @@
+#!/bin/sh
+# Test 'sort -u'.
+
+# 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 of the License, 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/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  sort --version
+fi
+
+. $srcdir/test-lib.sh
+
+cat > in <<\EOF
+1
+2
+1
+3
+EOF
+
+cat > exp <<\EOF
+1
+2
+3
+EOF
+
+for LOC in C "$LOCALE_FR" "$LOCALE_FR_UTF8"; do
+  test -z "$LOC" && continue
+
+  LC_ALL=$LOC sort -u in > out || { fail=1; break; }
+  compare exp out || { fail=1; break; }
+done
+
+Exit $fail