do not segfault if make_cache_entry failed

diff --git a/t/t4027-diff-submodule.sh b/t/t4027-diff-submodule.sh
index ba6679c6e4032bb12e4206226f95770946ece8cc..1c2edebb09bd6e1d7581365011c8500da57942c5 100755 (executable)
--- a/t/t4027-diff-submodule.sh
+++ b/t/t4027-diff-submodule.sh
@@ -3,7 +3,7 @@
 test_description='difference in submodules'
 
 . ./test-lib.sh
-. ../diff-lib.sh
+. "$TEST_DIRECTORY"/diff-lib.sh
 
 _z40=0000000000000000000000000000000000000000
 test_expect_success setup '