Merge pull request #364: Integrate git add with sparse-index

This follows #374 and #361 to complete the necessary functionality for the sparse-index experimental release.

This does not include the behavior changes requested upstream. The request is about how `git add` currently ignores changes that match a tracked path outside of the sparse-checkout definition. However, this is an established behavior of Git, so we don't need to change it for our dogfooders.

builtin/add.c

@@ -528,6 +528,9 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	add_new_files = !take_worktree_changes && !refresh_only && !add_renormalize;
 	require_pathspec = !(take_worktree_changes || (0 < addremove_explicit));
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 
 	/*

pathspec.c

@@ -37,8 +37,6 @@ void add_pathspec_matches_against_index(const struct pathspec *pathspec,
 			num_unmatched++;
 	if (!num_unmatched)
 		return;
-	/* TODO: audit for interaction with sparse-index. */
-	ensure_full_index(istate);
 	for (i = 0; i < istate->cache_nr; i++) {
 		const struct cache_entry *ce = istate->cache[i];
 		if (sw_action == PS_IGNORE_SKIP_WORKTREE && ce_skip_worktree(ce))

t/t1092-sparse-checkout-compatibility.sh

@@ -293,9 +293,6 @@ test_expect_success 'commit including unstaged changes' '
 test_expect_success 'status/add: outside sparse cone' '
 	init_repos &&
 
-	# adding a "missing" file outside the cone should fail
-	test_sparse_match test_must_fail git add folder1/a &&
-
 	# folder1 is at HEAD, but outside the sparse cone
 	run_on_sparse mkdir folder1 &&
 	cp initial-repo/folder1/a sparse-checkout/folder1/a &&
@@ -311,13 +308,6 @@ test_expect_success 'status/add: outside sparse cone' '
 
 	test_sparse_match git status --porcelain=v2 &&
 
-	# This "git add folder1/a" fails with a warning
-	# in the sparse repos, differing from the full
-	# repo. This is intentional.
-	test_sparse_match test_must_fail git add folder1/a &&
-	test_sparse_match test_must_fail git add --refresh folder1/a &&
-	test_all_match git status --porcelain=v2 &&
-
 	test_all_match git add . &&
 	test_all_match git status --porcelain=v2 &&
 	test_all_match git commit -m folder1/new &&
@@ -328,6 +318,25 @@ test_expect_success 'status/add: outside sparse cone' '
 	test_all_match git commit -m folder1/newer
 '
 
+test_expect_failure 'add: pathspec within sparse directory' '
+	init_repos &&
+
+	run_on_sparse mkdir folder1 &&
+	run_on_sparse ../edit-contents folder1/a &&
+	run_on_all ../edit-contents folder1/new &&
+
+	# This "git add folder1/a" fails with a warning
+	# in the sparse repos, differing from the full
+	# repo. This is intentional.
+	#
+	# However, in the sparse-index, folder1/a does not
+	# match any cache entry and fails with a different
+	# error message. This needs work.
+	test_sparse_match test_must_fail git add folder1/a &&
+	test_sparse_match test_must_fail git add --refresh folder1/a &&
+	test_all_match git status --porcelain=v2
+'
+
 test_expect_success 'checkout and reset --hard' '
 	init_repos &&
 
@@ -567,7 +576,14 @@ test_expect_success 'sparse-index is not expanded' '
 	git -C sparse-index reset --hard &&
 	ensure_not_expanded checkout rename-out-to-out -- deep/deeper1 &&
 	git -C sparse-index reset --hard &&
-	ensure_not_expanded restore -s rename-out-to-out -- deep/deeper1
+	ensure_not_expanded restore -s rename-out-to-out -- deep/deeper1 &&
+
+	echo >>sparse-index/README.md &&
+	ensure_not_expanded add -A &&
+	echo >>sparse-index/extra.txt &&
+	ensure_not_expanded add extra.txt &&
+	echo >>sparse-index/untracked.txt &&
+	ensure_not_expanded add .
 '
 
 test_expect_success 'reset mixed and checkout orphan' '