From: Victoria Dye <redacted>

Add tests focused on how 'git read-tree' behaves in sparse checkouts. Extra
emphasis is placed on interactions with files outside the sparse cone, e.g.
merges with out-of-cone conflicts.

Signed-off-by: Victoria Dye <redacted>
---
 t/perf/p2000-sparse-operations.sh        |  1 +
 t/t1092-sparse-checkout-compatibility.sh | 85 ++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/t/perf/p2000-sparse-operations.sh b/t/perf/p2000-sparse-operations.sh
index 2a7106b9495..382716cfca9 100755
--- a/t/perf/p2000-sparse-operations.sh
+++ b/t/perf/p2000-sparse-operations.sh

@@ -117,6 +117,7 @@ test_perf_on_all git diff
 test_perf_on_all git diff --cached
 test_perf_on_all git blame $SPARSE_CONE/a
 test_perf_on_all git blame $SPARSE_CONE/f3/a
+test_perf_on_all git read-tree -mu HEAD
 test_perf_on_all git checkout-index -f --all
 test_perf_on_all git update-index --add --remove $SPARSE_CONE/a
 

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index b1dcaa0e642..9d58da4e925 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh

@@ -819,6 +819,91 @@ test_expect_success 'update-index --cacheinfo' '
 	test_cmp expect sparse-checkout-out
 '
 
+test_expect_success 'read-tree --merge with files outside sparse definition' '
+	init_repos &&
+
+	test_all_match git checkout -b test-branch update-folder1 &&
+	for MERGE_TREES in "base HEAD update-folder2" \
+			   "update-folder1 update-folder2" \
+			   "update-folder2"
+	do
+		# Clean up and remove on-disk files
+		test_all_match git reset --hard HEAD &&
+		test_sparse_match git sparse-checkout reapply &&
+
+		# Although the index matches, without --no-sparse-checkout, outside-of-
+		# definition files will not exist on disk for sparse checkouts
+		test_all_match git read-tree -mu $MERGE_TREES &&
+		test_all_match git status --porcelain=v2 &&
+		test_path_is_missing sparse-checkout/folder2 &&
+		test_path_is_missing sparse-index/folder2 &&
+
+		test_all_match git read-tree --reset -u HEAD &&
+		test_all_match git status --porcelain=v2 &&
+
+		test_all_match git read-tree -mu --no-sparse-checkout $MERGE_TREES &&
+		test_all_match git status --porcelain=v2 &&
+		test_cmp sparse-checkout/folder2/a sparse-index/folder2/a &&
+		test_cmp sparse-checkout/folder2/a full-checkout/folder2/a || return 1
+	done
+'