submodule-config.c: use repo_get_oid for reading .gitmodules

diff --git a/t/t4053-diff-no-index.sh b/t/t4053-diff-no-index.sh
index 6e0dd6f9e5c482631147bb4770498dc4e7a8165f..4331b3118a07f900305fa783914091f73653bb45 100755 (executable)
--- a/t/t4053-diff-no-index.sh
+++ b/t/t4053-diff-no-index.sh
@@ -137,4 +137,12 @@ test_expect_success 'diff --no-index from repo subdir with absolute paths' '
        test_cmp expect actual
 '
 
+test_expect_success 'diff --no-index allows external diff' '
+       test_expect_code 1 \
+               env GIT_EXTERNAL_DIFF="echo external ;:" \
+               git diff --no-index non/git/a non/git/b >actual &&
+       echo external >expect &&
+       test_cmp expect actual
+'
+
 test_done