Function is_sparse_index_allowed

sparse-index.c:153–199

}

int is_sparse_index_allowed(struct index_state *istate, int flags)
{
	struct repo_config_values *cfg = repo_config_values(the_repository);

	if (!cfg->apply_sparse_checkout || !cfg->core_sparse_checkout_cone)
		return 0;

	if (!(flags & SPARSE_INDEX_MEMORY_ONLY)) {
		int test_env;

		/*
		 * The sparse index is not (yet) integrated with a split index.
		 */
		if (istate->split_index || git_env_bool("GIT_TEST_SPLIT_INDEX", 0))
			return 0;
		/*
		 * The GIT_TEST_SPARSE_INDEX environment variable triggers the
		 * index.sparse config variable to be on.
		 */
		test_env = git_env_bool("GIT_TEST_SPARSE_INDEX", -1);
		if (test_env >= 0)
			set_sparse_index_config(istate->repo, test_env);

		/*
		 * Only convert to sparse if index.sparse is set.
		 */
		prepare_repo_settings(istate->repo);
		if (!istate->repo->settings.sparse_index)
			return 0;
	}

	if (init_sparse_checkout_patterns(istate))
		return 0;

	/*
	 * We need cone-mode patterns to use sparse-index. If a user edits
	 * their sparse-checkout file manually, then we can detect during
	 * parsing that they are not actually using cone-mode patterns and
	 * hence we need to abort this conversion _without error_. Warnings
	 * already exist in the pattern parsing to inform the user of their
	 * bad patterns.
	 */
	if (!istate->sparse_checkout_patterns->use_cone_patterns)
		return 0;

	return 1;
}

int convert_to_sparse(struct index_state *istate, int flags)
{