t5543: atomic push reports exit code failure

Add new test cases in t5543 to avoid ignoring the exit code of
git-receive-pack(1) during atomic push with "--porcelain" flag.

We'd typically notice this case because the refs would have their error
message set. But there is an edge case when pushing refs succeeds, but
git-receive-pack(1) exits with a non-zero exit code at a later point in
time due to another error. An atomic git-push(1) would ignore that error
code, and consequently it would return successfully and not print any
error message at all.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5543-atomic-push.sh

@@ -280,4 +280,34 @@ test_expect_success 'atomic push reports (reject by non-ff)' '
 	test_cmp expect actual
 '
 
+test_expect_failure 'atomic push reports exit code failure' '
+	write_script receive-pack-wrapper <<-\EOF &&
+	git-receive-pack "$@"
+	exit 1
+	EOF
+	test_must_fail git -C workbench push --atomic \
+		--receive-pack="${SQ}$(pwd)${SQ}/receive-pack-wrapper" \
+		up HEAD:refs/heads/no-conflict 2>err &&
+	cat >expect <<-EOF &&
+	To ../upstream
+	 * [new branch]      HEAD -> no-conflict
+	error: failed to push some refs to ${SQ}../upstream${SQ}
+	EOF
+	test_cmp expect err
+'
+
+test_expect_failure 'atomic push reports exit code failure with porcelain' '
+	write_script receive-pack-wrapper <<-\EOF &&
+	git-receive-pack "$@"
+	exit 1
+	EOF
+	test_must_fail git -C workbench push --atomic --porcelain \
+		--receive-pack="${SQ}$(pwd)${SQ}/receive-pack-wrapper" \
+		up HEAD:refs/heads/no-conflict-porcelain 2>err &&
+	cat >expect <<-EOF &&
+	error: failed to push some refs to ${SQ}../upstream${SQ}
+	EOF
+	test_cmp expect err
+'
+
 test_done