t/t5505-remote: test failure of set-head

The test coverage was missing a test for the failure branch of remote
set-head auto's output. Add the missing text and while we are at it,
correct a small grammatical mistake in the error's output ("setup" is
the noun, "set up" is the verb).

Signed-off-by: Bence Ferdinandy <bence@ferdinandy.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: ferdinandyb

builtin/remote.c

@@ -1445,7 +1445,7 @@ static int set_head(int argc, const char **argv, const char *prefix)
 		if (!refs_ref_exists(get_main_ref_store(the_repository), buf2.buf))
 			result |= error(_("Not a valid ref: %s"), buf2.buf);
 		else if (refs_update_symref(get_main_ref_store(the_repository), buf.buf, buf2.buf, "remote set-head"))
-			result |= error(_("Could not setup %s"), buf.buf);
+			result |= error(_("Could not set up %s"), buf.buf);
 		else if (opt_a)
 			printf("%s/HEAD set to %s\n", argv[0], head_name);
 		free(head_name);

t/t5505-remote.sh

@@ -432,6 +432,18 @@ test_expect_success 'set-head --auto' '
 	)
 '
 
+test_expect_success REFFILES 'set-head --auto failure' '
+	test_when_finished "rm -f test/.git/refs/remotes/origin/HEAD.lock" &&
+	(
+		cd test &&
+		touch .git/refs/remotes/origin/HEAD.lock &&
+		test_must_fail git remote set-head --auto origin 2>err &&
+		tail -n1 err >output &&
+		echo "error: Could not set up refs/remotes/origin/HEAD" >expect &&
+		test_cmp expect output
+	)
+'
+
 test_expect_success 'set-head --auto has no problem w/multiple HEADs' '
 	(
 		cd test &&