gettext: setlocale(LC_CTYPE, "") breaks Git's C function assumptions

Remove the setlocale/LC_CTYPE call from gettext.c, we only need
setlocale/LC_MESSAGES to use the message catalog, and setting LC_CTYPE
from the environment breaks Git's assumptions about C library
functions.

Under a non-C locale functions like vsnprintf become locale sensitive,
so that they'll e.g. refuse to process ISO-8895-1 data under a UTF-8
locale.

This triggered a "your vsnprintf is broken" error on Git's own
repository when inspecting v0.99.6~1 under a UTF-8 locale.

That commit contains a ISO-8859-1 encoded author name, which the
locale aware vsnprintf(3) won't interpolate in the format argument,
due to mismatch between the data encoding and the locale.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gettext.c

@@ -17,6 +17,5 @@ extern void git_setup_gettext(void) {
 	}
 
 	(void)setlocale(LC_MESSAGES, "");
-	(void)setlocale(LC_CTYPE, "");
 	(void)textdomain("git");
 }

t/t0203-gettext-setlocale-sanity.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+#
+# Copyright (c) 2010 Ævar Arnfjörð Bjarmason
+#
+
+test_description="The Git C functions aren't broken by setlocale(3)"
+
+. ./lib-gettext.sh
+
+test_expect_success 'git show a ISO-8859-1 commit under C locale' '
+	. "$TEST_DIRECTORY"/t3901-8859-1.txt &&
+	test_commit "iso-c-commit" iso-under-c &&
+	git show >out 2>err &&
+	! test -s err &&
+	grep -q "iso-c-commit" out
+'
+
+test_expect_success GETTEXT_LOCALE 'git show a ISO-8859-1 commit under a UTF-8 locale' '
+	. "$TEST_DIRECTORY"/t3901-8859-1.txt &&
+	test_commit "iso-utf8-commit" iso-under-utf8 &&
+	LANGUAGE=is LC_ALL="$is_IS_locale" git show >out 2>err &&
+	! test -s err &&
+	grep -q "iso-utf8-commit" out
+'
+
+test_done