wt-status: expand added sparse directory entries

It is difficult, but possible, to get into a state where we intend to
add a directory that is outside of the sparse-checkout definition. Add a
test to t1092-sparse-checkout-compatibility.sh that demonstrates this
using a combination of 'git reset --mixed' and 'git checkout --orphan'.

This test failed before because the output of 'git status
--porcelain=v2' would not match on the lines for folder1/:

* The sparse-checkout repo (with a full index) would output each path
  name that is intended to be added.

* The sparse-index repo would only output that "folder1/" is staged for
  addition.

The status should report the full list of files to be added, and so this
sparse-directory entry should be expanded to a full list when reaching
it inside the wt_status_collect_changes_initial() method. Use
read_tree_at() to assist.

Somehow, this loop over the cache entries was not guarded by
ensure_full_index() as intended.

Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1092-sparse-checkout-compatibility.sh

@@ -524,4 +524,37 @@ test_expect_success 'sparse-index is not expanded' '
 	test_region ! index ensure_full_index trace2.txt
 '
 
+test_expect_success 'reset mixed and checkout orphan' '
+	init_repos &&
+
+	test_all_match git checkout rename-out-to-in &&
+
+	# Sparse checkouts do not agree with full checkouts about
+	# how to report a directory/file conflict during a reset.
+	# This command would fail with test_all_match because the
+	# full checkout reports "T folder1/0/1" while a sparse
+	# checkout reports "D folder1/0/1". This matches because
+	# the sparse checkouts skip "adding" the other side of
+	# the conflict.
+	test_sparse_match git reset --mixed HEAD~1 &&
+	test_sparse_match test-tool read-cache --table --expand &&
+	test_sparse_match git status --porcelain=v2 &&
+
+	# At this point, sparse-checkouts behave differently
+	# from the full-checkout.
+	test_sparse_match git checkout --orphan new-branch &&
+	test_sparse_match test-tool read-cache --table --expand &&
+	test_sparse_match git status --porcelain=v2
+'
+
+test_expect_success 'add everything with deep new file' '
+	init_repos &&
+
+	run_on_sparse git sparse-checkout set deep/deeper1/deepest &&
+
+	run_on_all touch deep/deeper1/x &&
+	test_all_match git add . &&
+	test_all_match git status --porcelain=v2
+'
+
 test_done

wt-status.c

@@ -657,6 +657,36 @@ static void wt_status_collect_changes_index(struct wt_status *s)
 	clear_pathspec(&rev.prune_data);
 }
 
+static int add_file_to_list(const struct object_id *oid,
+			    struct strbuf *base, const char *path,
+			    unsigned int mode, void *context)
+{
+	struct string_list_item *it;
+	struct wt_status_change_data *d;
+	struct wt_status *s = context;
+	struct strbuf full_name = STRBUF_INIT;
+
+	if (S_ISDIR(mode))
+		return READ_TREE_RECURSIVE;
+
+	strbuf_add(&full_name, base->buf, base->len);
+	strbuf_addstr(&full_name, path);
+	it = string_list_insert(&s->change, full_name.buf);
+	d = it->util;
+	if (!d) {
+		CALLOC_ARRAY(d, 1);
+		it->util = d;
+	}
+
+	d->index_status = DIFF_STATUS_ADDED;
+	/* Leave {mode,oid}_head zero for adds. */
+	d->mode_index = mode;
+	oidcpy(&d->oid_index, oid);
+	s->committable = 1;
+	strbuf_release(&full_name);
+	return 0;
+}
+
 static void wt_status_collect_changes_initial(struct wt_status *s)
 {
 	struct index_state *istate = s->repo->index;
@@ -671,6 +701,27 @@ static void wt_status_collect_changes_initial(struct wt_status *s)
 			continue;
 		if (ce_intent_to_add(ce))
 			continue;
+		if (S_ISSPARSEDIR(ce->ce_mode)) {
+			/*
+			 * This is a sparse directory entry, so we want to collect all
+			 * of the added files within the tree. This requires recursively
+			 * expanding the trees to find the elements that are new in this
+			 * tree and marking them with DIFF_STATUS_ADDED.
+			 */
+			struct strbuf base = STRBUF_INIT;
+			struct pathspec ps = { 0 };
+			struct tree *tree = lookup_tree(istate->repo, &ce->oid);
+
+			ps.recursive = 1;
+			ps.has_wildcard = 1;
+			ps.max_depth = -1;
+
+			strbuf_add(&base, ce->name, ce->ce_namelen);
+			read_tree_at(istate->repo, tree, &base, &ps,
+				     add_file_to_list, s);
+			continue;
+		}
+
 		it = string_list_insert(&s->change, ce->name);
 		d = it->util;
 		if (!d) {