t1092: add tests for 'git check-attr'

Add tests for `git check-attr`, make sure attribute file does get read
from index when path is either inside or outside of sparse-checkout
definition.

Add a test named 'diff --check with pathspec outside sparse definition'.
It starts by disabling the trailing whitespace and space-before-tab
checks using the core. whitespace configuration option. Then, it
specifically re-enables the trailing whitespace check for a file located
in a sparse directory by adding a whitespace=trailing-space rule to the
.gitattributes file within that directory. Next, create and populate the
folder1 directory, and then add the .gitattributes file to the index.
Edit the contents of folder1/a, add it to the index, and proceed to
"re-sparsify" 'folder1/' with 'git sparse-checkout reapply'. Finally,
use 'git diff --check --cached' to compare the 'index vs. HEAD',
ensuring the correct application of the attribute rules even when the
file's path is outside the sparse-checkout definition.

Mark the two tests 'check-attr with pathspec outside sparse definition'
and 'diff --check with pathspec outside sparse definition' as
'test_expect_failure' to reflect an existing issue where the attributes
inside a sparse directory are ignored. Ensure that the 'check-attr'
command fails to read the required attributes to demonstrate this
expected failure.

Helped-by: Victoria Dye <vdye@github.com>
Signed-off-by: Shuqi Liang <cheskaqiqi@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1092-sparse-checkout-compatibility.sh

@@ -2259,4 +2259,53 @@ test_expect_success 'worktree is not expanded' '
 	ensure_not_expanded worktree remove .worktrees/hotfix
 '
 
+test_expect_success 'check-attr with pathspec inside sparse definition' '
+	init_repos &&
+
+	echo "a -crlf myAttr" >>.gitattributes &&
+	run_on_all cp ../.gitattributes ./deep &&
+
+	test_all_match git check-attr -a -- deep/a &&
+
+	test_all_match git add deep/.gitattributes &&
+	test_all_match git check-attr -a --cached -- deep/a
+'
+
+test_expect_failure 'check-attr with pathspec outside sparse definition' '
+	init_repos &&
+
+	echo "a -crlf myAttr" >>.gitattributes &&
+	run_on_sparse mkdir folder1 &&
+	run_on_all cp ../.gitattributes ./folder1 &&
+	run_on_all cp a folder1/a &&
+
+	test_all_match git check-attr -a -- folder1/a &&
+
+	git -C full-checkout add folder1/.gitattributes &&
+	test_sparse_match git add --sparse folder1/.gitattributes &&
+	test_all_match git commit -m "add .gitattributes" &&
+	test_sparse_match git sparse-checkout reapply &&
+	test_all_match git check-attr -a --cached -- folder1/a
+'
+
+test_expect_failure 'diff --check with pathspec outside sparse definition' '
+	init_repos &&
+
+	write_script edit-contents <<-\EOF &&
+	echo "a " >"$1"
+	EOF
+
+	test_all_match git config core.whitespace -trailing-space,-space-before-tab &&
+
+	echo "a whitespace=trailing-space,space-before-tab" >>.gitattributes &&
+	run_on_all mkdir -p folder1 &&
+	run_on_all cp ../.gitattributes ./folder1 &&
+	test_all_match git add --sparse folder1/.gitattributes &&
+	run_on_all ../edit-contents folder1/a &&
+	test_all_match git add --sparse folder1/a &&
+
+	test_sparse_match git sparse-checkout reapply &&
+	test_all_match test_must_fail git diff --check --cached -- folder1/a
+'
+
 test_done