t5510: test the other side of the D/F conflict as well

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

Author: gitster

t/t5510-fetch.sh

@@ -59,6 +59,12 @@ test_expect_success "clone and setup child repos" '
 		cd case_sensitive_fd &&
 		git branch foo/bar &&
 		git branch Foo
+	) &&
+	git clone --ref-format=reftable . case_sensitive_df &&
+	(
+		cd case_sensitive_df &&
+		git branch Foo/bar &&
+		git branch foo
 	)
 '
 
@@ -1566,6 +1572,20 @@ test_expect_success CASE_INSENSITIVE_FS,REFFILES 'F/D conflict on case insensiti
 	)
 '
 
+test_expect_success CASE_INSENSITIVE_FS,REFFILES 'D/F conflict on case insensitive filesystem' '
+	test_when_finished rm -rf case_insensitive &&
+	(
+		git init --bare case_insensitive &&
+		cd case_insensitive &&
+		git remote add origin -- ../case_sensitive_df &&
+		test_must_fail git fetch -f origin "refs/heads/*:refs/heads/*" 2>err &&
+		test_grep "failed: refname conflict" err &&
+		git rev-parse refs/heads/main >expect &&
+		git rev-parse refs/heads/Foo/bar >actual &&
+		test_cmp expect actual
+	)
+'
+
 . "$TEST_DIRECTORY"/lib-httpd.sh
 start_httpd