t4214: use test_merge

In the previous commit, we extended test_merge() so that it could
perform octopus merges. Now that the restriction is lifted, use
test_merge() to perform the octopus merge instead of manually
duplicating test_merge() functionality.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4214-log-graph-octopus.sh

diff --git a/t/t4214-log-graph-octopus.sh b/t/t4214-log-graph-octopus.sh
index dab96c8..f6e22ec 100755
--- a/t/t4214-log-graph-octopus.sh
+++ b/t/t4214-log-graph-octopus.sh
@@ -41,8 +41,7 @@
 		test_commit $i $i $i tag$i || return $?
 	done &&
 	git checkout 1 -b merge &&
-	test_tick &&
-	git merge -m octopus-merge 1 2 3 4 &&
+	test_merge octopus-merge 1 2 3 4 &&
 	git checkout 1 -b L &&
 	test_commit left
 '