Merge branch 'vd/sparse-read-tree'

"git read-tree" has been made to be aware of the sparse-index
feature.

* vd/sparse-read-tree:
  read-tree: make three-way merge sparse-aware
  read-tree: make two-way merge sparse-aware
  read-tree: narrow scope of index expansion for '--prefix'
  read-tree: integrate with sparse index
  read-tree: expand sparse checkout test coverage
  read-tree: explicitly disallow prefixes with a leading '/'
  status: fix nested sparse directory diff in sparse index
  sparse-index: prevent repo root from becoming sparse

3 files changed, 144 insertions, 0 deletions

diff --git a/t/perf/p2000-sparse-operations.sh b/t/perf/p2000-sparse-operations.sh
index 2a7106b949..382716cfca 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/t1003-read-tree-prefix.sh b/t/t1003-read-tree-prefix.sh
index e0db2066f3..c860c08ecb 100755
--- a/t/t1003-read-tree-prefix.sh
+++ b/t/t1003-read-tree-prefix.sh
@@ -25,4 +25,14 @@ test_expect_success 'read-tree --prefix' '
 	cmp expect actual
 '
 
+test_expect_success 'read-tree --prefix with leading slash exits with error' '
+	git rm -rf . &&
+	test_must_fail git read-tree --prefix=/two/ $tree &&
+	git read-tree --prefix=two/ $tree &&
+
+	git rm -rf . &&
+	test_must_fail git read-tree --prefix=/ $tree &&
+	git read-tree --prefix= $tree
+'
+
 test_done
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 2a04b532f9..dcc0a30d4a 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -244,6 +244,24 @@ test_expect_success 'expanded in-memory index matches full index' '
 	test_sparse_match git ls-files --stage
 '
 
+test_expect_success 'root directory cannot be sparse' '
+	init_repos &&
+
+	# Remove all in-cone files and directories from the index, collapse index
+	# with `git sparse-checkout reapply`
+	git -C sparse-index rm -r . &&
+	git -C sparse-index sparse-checkout reapply &&
+
+	# Verify sparse directories still present, root directory is not sparse
+	cat >expect <<-EOF &&
+	folder1/
+	folder2/
+	x/
+	EOF
+	git -C sparse-index ls-files --sparse >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'status with options' '
 	init_repos &&
 	test_sparse_match ls &&
@@ -260,6 +278,13 @@ test_expect_success 'status with options' '
 	test_all_match git status --porcelain=v2 -uno
 '
 
+test_expect_success 'status with diff in unexpanded sparse directory' '
+	init_repos &&
+	test_all_match git checkout rename-base &&
+	test_all_match git reset --soft rename-out-to-out &&
+	test_all_match git status --porcelain=v2
+'
+
 test_expect_success 'status reports sparse-checkout' '
 	init_repos &&
 	git -C sparse-checkout status >full &&
@@ -794,6 +819,93 @@ test_expect_success 'update-index --cacheinfo' '
 	test_cmp expect sparse-checkout-out
 '
 
+for MERGE_TREES in "base HEAD update-folder2" \
+		   "update-folder1 update-folder2" \
+		   "update-folder2"
+do
+	test_expect_success "'read-tree -mu $MERGE_TREES' with files outside sparse definition" '
+		init_repos &&
+
+		# 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
+
+	'
+done
+
+test_expect_success 'read-tree --merge with edit/edit conflicts in sparse directories' '
+	init_repos &&
+
+	# Merge of multiple changes to same directory (but not same files) should
+	# succeed
+	test_all_match git read-tree -mu base rename-base update-folder1 &&
+	test_all_match git status --porcelain=v2 &&
+
+	test_all_match git reset --hard &&
+
+	test_all_match git read-tree -mu rename-base update-folder2 &&
+	test_all_match git status --porcelain=v2 &&
+
+	test_all_match git reset --hard &&
+
+	test_all_match test_must_fail git read-tree -mu base update-folder1 rename-out-to-in &&
+	test_all_match test_must_fail git read-tree -mu rename-out-to-in update-folder1
+'
+
+test_expect_success 'read-tree --prefix' '
+	init_repos &&
+
+	# If files differing between the index and target <commit-ish> exist
+	# inside the prefix, `read-tree --prefix` should fail
+	test_all_match test_must_fail git read-tree --prefix=deep/ deepest &&
+	test_all_match test_must_fail git read-tree --prefix=folder1/ update-folder1 &&
+
+	# If no differing index entries exist matching the prefix,
+	# `read-tree --prefix` updates the index successfully
+	test_all_match git rm -rf deep/deeper1/deepest/ &&
+	test_all_match git read-tree --prefix=deep/deeper1/deepest -u deepest &&
+	test_all_match git status --porcelain=v2 &&
+
+	test_all_match git rm -rf --sparse folder1/ &&
+	test_all_match git read-tree --prefix=folder1/ -u update-folder1 &&
+	test_all_match git status --porcelain=v2 &&
+
+	test_all_match git rm -rf --sparse folder2/0 &&
+	test_all_match git read-tree --prefix=folder2/0/ -u rename-out-to-out &&
+	test_all_match git status --porcelain=v2
+'
+
+test_expect_success 'read-tree --merge with directory-file conflicts' '
+	init_repos &&
+
+	test_all_match git checkout -b test-branch rename-base &&
+
+	# Although the index matches, without --no-sparse-checkout, outside-of-
+	# definition files will not exist on disk for sparse checkouts
+	test_sparse_match git read-tree -mu rename-out-to-out &&
+	test_sparse_match git status --porcelain=v2 &&
+	test_path_is_missing sparse-checkout/folder2 &&
+	test_path_is_missing sparse-index/folder2 &&
+
+	test_sparse_match git read-tree --reset -u HEAD &&
+	test_sparse_match git status --porcelain=v2 &&
+
+	test_sparse_match git read-tree -mu --no-sparse-checkout rename-out-to-out &&
+	test_sparse_match git status --porcelain=v2 &&
+	test_cmp sparse-checkout/folder2/0/1 sparse-index/folder2/0/1
+'
+
 test_expect_success 'merge, cherry-pick, and rebase' '
 	init_repos &&
 
@@ -1297,6 +1409,27 @@ test_expect_success 'sparse index is not expanded: fetch/pull' '
 	ensure_not_expanded pull full base
 '
 
+test_expect_success 'sparse index is not expanded: read-tree' '
+	init_repos &&
+
+	ensure_not_expanded checkout -b test-branch update-folder1 &&
+	for MERGE_TREES in "base HEAD update-folder2" \
+			   "base HEAD rename-base" \
+			   "base update-folder2" \
+			   "base rename-base" \
+			   "update-folder2"
+	do
+		ensure_not_expanded read-tree -mu $MERGE_TREES &&
+		ensure_not_expanded reset --hard || return 1
+	done &&
+
+	rm -rf sparse-index/deep/deeper2 &&
+	ensure_not_expanded add . &&
+	ensure_not_expanded commit -m "test" &&
+
+	ensure_not_expanded read-tree --prefix=deep/deeper2 -u deepest
+'
+
 test_expect_success 'ls-files' '
 	init_repos &&