Re: [PATCH v9 5/9] rebase: refactor can_fast_forward into goto tower

> Before, can_fast_forward was written with an if-else statement. However,
> in the future, we may be adding more termination cases which would lead
> to deeply nested if statements.
> 
> Refactor to use a goto tower so that future cases can be easily
> inserted.
> 
> Signed-off-by: Denton Liu <liu.denton@gmail.com>
> ---
>  builtin/rebase.c | 24 +++++++++++++++---------
>  1 file changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 670096c065..22c4f1ff93 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -1264,21 +1264,27 @@ static int can_fast_forward(struct commit *onto, struct object_id *head_oid,
>  			    struct object_id *merge_base)
>  {
>  	struct commit *head = lookup_commit(the_repository, head_oid);
> -	struct commit_list *merge_bases;
> -	int res;
> +	struct commit_list *merge_bases = NULL;
> +	int res = 0;
>  
>  	if (!head)
> -		return 0;
> +		goto done;
>  
>  	merge_bases = get_merge_bases(onto, head);
> -	if (merge_bases && !merge_bases->next) {
> -		oidcpy(merge_base, &merge_bases->item->object.oid);
> -		res = oideq(merge_base, &onto->object.oid);
> -	} else {
> +	if (!merge_bases || merge_bases->next) {
>  		oidcpy(merge_base, &null_oid);
> -		res = 0;
> +		goto done;
>  	}
> -	free_commit_list(merge_bases);
> +
> +	oidcpy(merge_base, &merge_bases->item->object.oid);
> +	if (!oideq(merge_base, &onto->object.oid))
> +		goto done;
> +
> +	res = 1;
> +
> +done:
> +	if (merge_bases)
> +		free_commit_list(merge_bases);