[PATCH v1 3/3] check-attr: integrate with sparse-index

[Shuqi Liang <cheskaqiqi@gmail.com>]

Set the requires-full-index to false for "diff-tree".

Add test to ensure the index is not expanded when the
sparse index is enabled.

The `p2000` tests demonstrate a ~63% execution time reduction for
'git check-attr' using a sparse index.

Test                                            before  after
-----------------------------------------------------------------------
2000.106: git check-attr -a f2/f4/a (full-v3)    0.05   0.05 +0.0%
2000.107: git check-attr -a f2/f4/a (full-v4)    0.05   0.05 +0.0%
2000.108: git check-attr -a f2/f4/a (sparse-v3)  0.04   0.02 -50.0%
2000.109: git check-attr -a f2/f4/a (sparse-v4)  0.04   0.01 -75.0%

Helped-by: Victoria Dye <vdye@github.com>
Signed-off-by: Shuqi Liang <cheskaqiqi@gmail.com>
---
 builtin/check-attr.c                     |  3 +++
 t/t1092-sparse-checkout-compatibility.sh | 11 +++++++++++
 2 files changed, 14 insertions(+)

diff --git a/builtin/check-attr.c b/builtin/check-attr.c
index b22ff748c3..02267f9bc1 100644
--- a/builtin/check-attr.c
+++ b/builtin/check-attr.c
@@ -122,6 +122,9 @@ int cmd_check_attr(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, check_attr_options,
 			     check_attr_usage, PARSE_OPT_KEEP_DASHDASH);
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+	
 	if (repo_read_index(the_repository) < 0) {
 		die("invalid cache");
 	}
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 4edfa3c168..317ccc8ec5 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -2288,4 +2288,15 @@ test_expect_success 'check-attr with pathspec outside sparse definition' '
 	test_all_match git check-attr  -a --cached -- folder1/a
 '
 
+test_expect_success 'sparse-index is not expanded: check-attr' '
+	init_repos &&
+
+	echo "a -crlf myAttr" >>.gitattributes &&
+	run_on_all cp ../.gitattributes ./deep &&
+
+	ensure_not_expanded check-attr -a -- deep/a &&
+	run_on_all git add deep/.gitattributes &&
+	ensure_not_expanded check-attr -a --cached -- deep/a
+'
+
 test_done
-- 
2.39.0