repo-settings: enable sparse index by default

There is some strangeness when expanding a sparse-index that exists
within a submodule. We will need to resolve that later, but for now,
let's do a better job of explicitly disabling the sparse-index when
requested, and do so in t7817.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

repo-settings.c

@@ -95,9 +95,9 @@ void prepare_repo_settings(struct repository *r)
 	r->settings.command_requires_full_index = 1;
 
 	/*
-	 * Initialize this as off.
+	 * Initialize this as on.
 	 */
-	r->settings.sparse_index = 0;
-	if (!repo_config_get_bool(r, "index.sparse", &value) && value)
-		r->settings.sparse_index = 1;
+	r->settings.sparse_index = 1;
+	if (!repo_config_get_bool(r, "index.sparse", &value) && !value)
+		r->settings.sparse_index = 0;
 }

sparse-index.c

@@ -105,7 +105,7 @@ int set_sparse_index_config(struct repository *repo, int enable)
 	char *config_path = repo_git_path(repo, "config.worktree");
 	res = git_config_set_in_file_gently(config_path,
 					    "index.sparse",
-					    enable ? "true" : NULL);
+					    enable ? "true" : "false");
 	free(config_path);
 
 	prepare_repo_settings(repo);

t/t1091-sparse-checkout-builtin.sh

@@ -215,7 +215,7 @@ test_expect_success 'sparse-index enabled and disabled' '
 	test-tool -C repo read-cache --table >cache &&
 	! grep " tree " cache &&
 	git -C repo config --list >config &&
-	! grep index.sparse config
+	test_cmp_config -C repo false index.sparse
 '
 
 test_expect_success 'cone mode: init and set' '

t/t1092-sparse-checkout-compatibility.sh

@@ -147,6 +147,7 @@ init_repos () {
 	git -C sparse-index reset --hard &&
 
 	# initialize sparse-checkout definitions
+	git -C sparse-checkout config index.sparse false &&
 	git -C sparse-checkout sparse-checkout init --cone &&
 	git -C sparse-checkout sparse-checkout set deep &&
 	git -C sparse-index sparse-checkout init --cone --sparse-index &&

t/t7817-grep-sparse-checkout.sh

@@ -49,7 +49,7 @@ test_expect_success 'setup' '
 		echo "text" >B/b &&
 		git add A B &&
 		git commit -m sub &&
-		git sparse-checkout init --cone &&
+		git sparse-checkout init --cone --no-sparse-index &&
 		git sparse-checkout set B
 	) &&