Function grep_submodule

builtin/grep.c:446–546

		     int check_attr);

static int grep_submodule(struct grep_opt *opt,
			  const struct pathspec *pathspec,
			  const struct object_id *oid,
			  const char *filename, const char *path, int cached)
{
	struct repository *subrepo;
	struct repository *superproject = opt->repo;
	struct grep_opt subopt;
	int hit = 0;

	if (!is_submodule_active(superproject, path))
		return 0;

	subrepo = xmalloc(sizeof(*subrepo));
	if (repo_submodule_init(subrepo, superproject, path, null_oid(opt->repo->hash_algo))) {
		free(subrepo);
		return 0;
	}
	ALLOC_GROW(repos_to_free, repos_to_free_nr + 1, repos_to_free_alloc);
	repos_to_free[repos_to_free_nr++] = subrepo;

	/*
	 * NEEDSWORK: repo_read_gitmodules() might call
	 * odb_add_to_alternates_memory() via config_from_gitmodules(). This
	 * operation causes a race condition with concurrent object readings
	 * performed by the worker threads. That's why we need obj_read_lock()
	 * here. It should be removed once it's no longer necessary to add the
	 * subrepo's odbs to the in-memory alternates list.
	 */
	obj_read_lock();

	/*
	 * NEEDSWORK: when reading a submodule, the sparsity settings in the
	 * superproject are incorrectly forgotten or misused. For example:
	 *
	 * 1. "command_requires_full_index"
	 * 	When this setting is turned on for `grep`, only the superproject
	 *	knows it. All the submodules are read with their own configs
	 *	and get prepare_repo_settings()'d. Therefore, these submodules
	 *	"forget" the sparse-index feature switch. As a result, the index
	 *	of these submodules are expanded unexpectedly.
	 *
	 * 2. "config_values_private_.apply_sparse_checkout"
	 *	When running `grep` in the superproject, this setting is
	 *	populated using the superproject's configs. However, once
	 *	initialized, this config is globally accessible and is read by
	 *	prepare_repo_settings() for the submodules. For instance, if a
	 *	submodule is using a sparse-checkout, however, the superproject
	 *	is not, the result is that the config from the superproject will
	 *	dictate the behavior for the submodule, making it "forget" its
	 *	sparse-checkout state.
	 *
	 * 3. "core_sparse_checkout_cone"
	 *	ditto.
	 *
	 * Note that this list is not exhaustive.
	 */
	repo_read_gitmodules(subrepo, 0);