Re: [PATCH v4 4/7] sequencer: handle unborn branch with `--allow-empty`

> +	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL)) {
> +		/*
> +		 * Check to see if this is an unborn branch
> +		 */
> +		head_name = resolve_ref_unsafe("HEAD", RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE, &head_oid, NULL);
> +		if (!head_name || !starts_with(head_name, "refs/heads/") || !is_null_oid(&head_oid))
> +			return error(_("could not resolve HEAD commit"));
> +		head_tree_oid = the_hash_algo->empty_tree;
> +	} else {
> +		head_commit = lookup_commit(r, &head_oid);
>  
> -	head_commit = lookup_commit(r, &head_oid);
> +		/*
> +		 * If head_commit is NULL, check_commit, called from
> +		 * lookup_commit, would have indicated that head_commit is not
> +		 * a commit object already.  repo_parse_commit() will return failure
> +		 * without further complaints in such a case.  Otherwise, if
> +		 * the commit is invalid, repo_parse_commit() will complain.  So
> +		 * there is nothing for us to say here.  Just return failure.
> +		 */
> +		if (repo_parse_commit(r, head_commit))
> +			return -1;