Function split_commit

builtin/history.c:785–898

}

static int split_commit(struct repository *repo,
			struct commit *original,
			struct pathspec *pathspec,
			struct commit **out)
{
	struct interactive_options interactive_opts = INTERACTIVE_OPTIONS_INIT;
	struct strbuf index_file = STRBUF_INIT;
	struct index_state index = INDEX_STATE_INIT(repo);
	const struct object_id *original_commit_tree_oid;
	const struct object_id *old_tree_oid, *new_tree_oid;
	struct object_id parent_tree_oid;
	char original_commit_oid[GIT_MAX_HEXSZ + 1];
	struct commit *first_commit, *second_commit;
	struct commit_list *parents = NULL;
	struct tree *split_tree;
	int ret;

	if (original->parents) {
		if (repo_parse_commit(repo, original->parents->item)) {
			ret = error(_("unable to parse parent commit %s"),
				    oid_to_hex(&original->parents->item->object.oid));
			goto out;
		}

		parent_tree_oid = *get_commit_tree_oid(original->parents->item);
	} else {
		oidcpy(&parent_tree_oid, repo->hash_algo->empty_tree);
	}
	original_commit_tree_oid = get_commit_tree_oid(original);

	/*
	 * Construct the first commit. This is done by taking the original
	 * commit parent's tree and selectively patching changes from the diff
	 * between that parent and its child.
	 */
	repo_git_path_replace(repo, &index_file, "%s", "history-split.index");

	ret = write_ondisk_index(repo, &parent_tree_oid, index_file.buf);
	if (ret < 0)
		goto out;

	ret = read_index_from(&index, index_file.buf, repo->gitdir);
	if (ret < 0) {
		ret = error(_("failed reading temporary index"));
		goto out;
	}

	oid_to_hex_r(original_commit_oid, &original->object.oid);
	ret = run_add_p_index(repo, &index, index_file.buf, &interactive_opts,
			      original_commit_oid, pathspec, ADD_P_DISALLOW_EDIT);
	if (ret < 0)
		goto out;

	split_tree = write_in_core_index_as_tree(repo, &index);
	if (!split_tree) {
		ret = error(_("failed split tree"));
		goto out;
	}