Changes since v9:

* Replace the unhelpful test with a double-dash case to prevent
regressions. 

* Remove the unmodified test because its empty output could pass
even with an index expansion issue.

* Update the relevant commit message.

* Did not add " -- " in modified test as suggested sine 
"folder1/a" exists in the working tree


Shuqi Liang (2):
  t1092: add tests for `git diff-files`
  diff-files: integrate with sparse index

 builtin/diff-files.c                     |  4 ++
 t/perf/p2000-sparse-operations.sh        |  2 +
 t/t1092-sparse-checkout-compatibility.sh | 66 +++++++++++++++++++++++-
 3 files changed, 70 insertions(+), 2 deletions(-)

Range-diff against v9:
1:  d78513af83 ! 1:  3b284bdf3b t1092: add tests for `git diff-files`
    @@ Commit message
         make a directory called 'folder1' and copy `a` into 'folder1/a'.
         'folder1/a' is identical to `a` in the base commit. These make
         'folder1/a' in the index, while leaving it outside of the
    -    sparse-checkout definition. Test 'folder1/a'being present on-disk
    -    without modifications, then change content inside 'folder1/a' in order
    +    sparse-checkout definition. Change content inside 'folder1/a' in order
         to test 'folder1/a' being present on-disk with modifications.
     
         Signed-off-by: Shuqi Liang [off-list ref]
    @@ t/t1092-sparse-checkout-compatibility.sh: test_expect_success 'sparse-index is n
     +test_expect_success 'diff-files with pathspec outside sparse definition' '
     +	init_repos &&
     +
    -+	test_sparse_match test_must_fail git diff-files folder2/a &&
    ++	test_sparse_match git diff-files -- folder2/a &&
     +
     +	write_script edit-contents <<-\EOF &&
     +	echo text >>"$1"
    @@ t/t1092-sparse-checkout-compatibility.sh: test_expect_success 'sparse-index is n
     +	run_on_all mkdir -p folder1 &&
     +	run_on_all cp a folder1/a &&
     +
    -+	# file present on-disk without modifications
    -+	# use `--stat` to ignore file creation time differences in
    -+	# unrefreshed index
    -+	test_all_match git diff-files --stat &&
    -+	test_all_match git diff-files --stat folder1/a &&
    -+	test_all_match git diff-files --stat "folder*/a" &&
    -+
     +	# file present on-disk with modifications
     +	run_on_all ../edit-contents folder1/a &&
     +	test_all_match git diff-files &&
2:  a2454befa0 = 2:  15472db302 diff-files: integrate with sparse index
-- 
2.39.0