t5318: reorder test below 'graph_read_expect'

In the subsequent commit, we will introduce a dependency on
'graph_read_expect' from t5318.7. Preemptively move it below
'graph_read_expect()'s definition so that the test can call it.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5318-commit-graph.sh

@@ -42,15 +42,6 @@ test_expect_success 'create commits and repack' '
 	git repack
 '
 
-test_expect_success 'exit with correct error on bad input to --stdin-commits' '
-	cd "$TRASH_DIRECTORY/full" &&
-	echo HEAD | test_expect_code 1 git commit-graph write --stdin-commits 2>stderr &&
-	test_i18ngrep "unexpected non-hex object ID: HEAD" stderr &&
-	# valid tree OID, but not a commit OID
-	git rev-parse HEAD^{tree} | test_expect_code 1 git commit-graph write --stdin-commits 2>stderr &&
-	test_i18ngrep "invalid commit object id" stderr
-'
-
 graph_git_two_modes() {
 	git -c core.commitGraph=true $1 >output
 	git -c core.commitGraph=false $1 >expect
@@ -91,6 +82,15 @@ graph_read_expect() {
 	test_cmp expect output
 }
 
+test_expect_success 'exit with correct error on bad input to --stdin-commits' '
+	cd "$TRASH_DIRECTORY/full" &&
+	echo HEAD | test_expect_code 1 git commit-graph write --stdin-commits 2>stderr &&
+	test_i18ngrep "unexpected non-hex object ID: HEAD" stderr &&
+	# valid tree OID, but not a commit OID
+	git rev-parse HEAD^{tree} | test_expect_code 1 git commit-graph write --stdin-commits 2>stderr &&
+	test_i18ngrep "invalid commit object id" stderr
+'
+
 test_expect_success 'write graph' '
 	cd "$TRASH_DIRECTORY/full" &&
 	git commit-graph write &&