t9129: fix UTF-8 locale detection

The UTF-8 prerequisite test checked explicitly for en_US.utf8 in the
output from "locale -a", but the tests that are actually protected by the
prerequisite were asking LC_ALL=en_US.UTF-8 from the system.

This inconsistency leads the tests to fail on platforms that do not know
both en_US.UTF-8 and en_US.utf8 (thanks you, Yann Droneaud, for bringing
this up with an initial patch).

Instead, pick a locale with ".UTF-8" (with or without hyphen, spelled in
either upper or lowercase) in its name from "locale -a" output, and use it
for running the test.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9129-git-svn-i18n-commitencoding.sh

@@ -14,10 +14,22 @@ compare_git_head_with () {
 	test_cmp current "$1"
 }
 
+a_utf8_locale=$(locale -a | sed -n '/\.[uU][tT][fF]-*8$/{
+	p
+	q
+}')
+
+if test -n "$a_utf8_locale"
+then
+	test_set_prereq UTF8
+else
+	say "UTF-8 locale not available, some tests are skipped"
+fi
+
 compare_svn_head_with () {
 	# extract just the log message and strip out committer info.
 	# don't use --limit here since svn 1.1.x doesn't have it,
-	LC_ALL=en_US.UTF-8 svn log `git svn info --url` | perl -w -e '
+	LC_ALL="$a_utf8_locale" svn log `git svn info --url` | perl -w -e '
 		use bytes;
 		$/ = ("-"x72) . "\n";
 		my @x = <STDIN>;
@@ -69,12 +81,6 @@ do
 	'
 done
 
-if locale -a |grep -q en_US.utf8; then
-	test_set_prereq UTF8
-else
-	say "UTF-8 locale not available, test skipped"
-fi
-
 test_expect_success UTF8 'ISO-8859-1 should match UTF-8 in svn' '
 	(
 		cd ISO8859-1 &&