cache-tree: reject entries with null sha1

diff --git a/t/t7009-filter-branch-null-sha1.sh b/t/t7009-filter-branch-null-sha1.sh
index c27f90f285faf0529f08fae7262a40b605bd7375..a8d9ec498778b5a597fd5751f811c8bf0b0ab926 100755 (executable)
--- a/t/t7009-filter-branch-null-sha1.sh
+++ b/t/t7009-filter-branch-null-sha1.sh
@@ -31,6 +31,12 @@ test_expect_success 'setup: bring HEAD and index in sync' '
        git commit -a -m "back to normal"
 '
 
+test_expect_success 'noop filter-branch complains' '
+       test_must_fail git filter-branch \
+               --force --prune-empty \
+               --index-filter "true"
+'
+
 test_expect_success 'filter commands are still checked' '
        test_must_fail git filter-branch \
                --force --prune-empty \