sparse-index: make non-mixed reset sparse-aware

This change allows non-mixed resets to no longer require that the full index
is expanded. This is accomplished by updating the `prime_cache_tree_rec`
function to have it reconstruct the cache tree "aware" of whether a directory
is sparse in the index or not. This check must be done by verifying the
contents of the cache itself (rather than checking whether a directory is
inside of the sparse checkout cone) as entries may have been added to the
sparse index outside of the checkout cone.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

cache-tree.c

@@ -777,13 +777,31 @@ int write_index_as_tree(struct object_id *oid, struct index_state *index_state,
 
 static void prime_cache_tree_rec(struct repository *r,
 				 struct cache_tree *it,
-				 struct tree *tree)
+				 struct tree *tree,
+				 struct strbuf *tree_path)
 {
+	struct strbuf subtree_path = STRBUF_INIT;
 	struct tree_desc desc;
 	struct name_entry entry;
 	int cnt;
 
 	oidcpy(&it->oid, &tree->object.oid);
+
+	/*
+	 * If this entry is outside the sparse-checkout cone, then it might be
+	 * a sparse directory entry. Check the index to ensure it is by looking
+	 * for an entry with the exact same name as the tree. If no matching sparse
+	 * entry is found, a staged or conflicted entry is preventing this
+	 * directory from collapsing to a sparse directory entry, so the cache
+	 * tree expansion should continue.
+	 */
+	if (r->index->sparse_index &&
+	    !path_in_cone_modesparse_checkout(tree_path->buf, r->index) &&
+	    index_name_pos(r->index, tree_path->buf, tree_path->len) >= 0) {
+		it->entry_count = 1;
+		return;
+	}
+
 	init_tree_desc(&desc, tree->buffer, tree->size);
 	cnt = 0;
 	while (tree_entry(&desc, &entry)) {
@@ -792,27 +810,38 @@ static void prime_cache_tree_rec(struct repository *r,
 		else {
 			struct cache_tree_sub *sub;
 			struct tree *subtree = lookup_tree(r, &entry.oid);
+
 			if (!subtree->object.parsed)
 				parse_tree(subtree);
 			sub = cache_tree_sub(it, entry.path);
 			sub->cache_tree = cache_tree();
-			prime_cache_tree_rec(r, sub->cache_tree, subtree);
+			strbuf_reset(&subtree_path);
+			strbuf_grow(&subtree_path, tree_path->len + entry.pathlen + 1);
+			strbuf_addbuf(&subtree_path, tree_path);
+			strbuf_add(&subtree_path, entry.path, entry.pathlen);
+			strbuf_addch(&subtree_path, '/');
+
+			prime_cache_tree_rec(r, sub->cache_tree, subtree, &subtree_path);
 			cnt += sub->cache_tree->entry_count;
 		}
 	}
 	it->entry_count = cnt;
+
+	strbuf_release(&subtree_path);
 }
 
 void prime_cache_tree(struct repository *r,
 		      struct index_state *istate,
 		      struct tree *tree)
 {
+	struct strbuf tree_path = STRBUF_INIT;
+
 	trace2_region_enter("cache-tree", "prime_cache_tree", r);
 	cache_tree_free(&istate->cache_tree);
 	istate->cache_tree = cache_tree();
 
-	ensure_full_index(istate);
-	prime_cache_tree_rec(r, istate->cache_tree, tree);
+	prime_cache_tree_rec(r, istate->cache_tree, tree, &tree_path);
+	strbuf_release(&tree_path);
 	istate->cache_changed |= CACHE_TREE_CHANGED;
 	trace2_region_leave("cache-tree", "prime_cache_tree", r);
 }

t/t1092-sparse-checkout-compatibility.sh

@@ -787,9 +787,9 @@ test_expect_success 'sparse-index is not expanded' '
 	ensure_not_expanded checkout - &&
 	ensure_not_expanded switch rename-out-to-out &&
 	ensure_not_expanded switch - &&
-	git -C sparse-index reset --hard &&
+	ensure_not_expanded reset --hard &&
 	ensure_not_expanded checkout rename-out-to-out -- deep/deeper1 &&
-	git -C sparse-index reset --hard &&
+	ensure_not_expanded reset --hard &&
 	ensure_not_expanded restore -s rename-out-to-out -- deep/deeper1 &&
 
 	echo >>sparse-index/README.md &&
@@ -799,6 +799,17 @@ test_expect_success 'sparse-index is not expanded' '
 	echo >>sparse-index/untracked.txt &&
 	ensure_not_expanded add . &&
 
+	for ref in update-deep update-folder1 update-folder2 update-deep
+	do
+		echo >>sparse-index/README.md &&
+		ensure_not_expanded reset --hard $ref
+	done &&
+
+	ensure_not_expanded reset --hard update-deep &&
+	ensure_not_expanded reset --keep base &&
+	ensure_not_expanded reset --merge update-deep &&
+	ensure_not_expanded reset --hard &&
+
 	ensure_not_expanded checkout -f update-deep &&
 	(
 		sane_unset GIT_TEST_MERGE_ALGORITHM &&