Re: [PATCH v6 05/32] refs: add a backend method structure with transaction functions

[Jeff King <peff@peff.net>]

On Wed, Feb 24, 2016 at 05:58:37PM -0500, David Turner wrote:

> +int set_ref_storage_backend(const char *name)
> +{
> +	struct ref_storage_be *be;
> +
> +	for (be = refs_backends; be; be = be->next)
> +		if (!strcmp(be->name, name)) {
> +			the_refs_backend = be;
> +			return 0;
> +		}
> +	return 1;
> +}

So we search through the list and assign the_refs_backend if we find
something, returning 0 for success, and 1 if we found nothing. OK
(though our usual convention is that if 0 is success, -1 is the error
case).

> +int ref_storage_backend_exists(const char *name)
> +{
> +	struct ref_storage_be *be;
> +
> +	for (be = refs_backends; be; be = be->next)
> +		if (!strcmp(be->name, name)) {
> +			the_refs_backend = be;
> +			return 1;
> +		}
> +	return 0;
> +}

Here we do the same thing, but we get "1" for exists, and "0"
otherwise. That makes sense if this is about querying for existence. But
why does the query function still set the_refs_backend?

I'm guessing the assignment in the second one is just copy-pasta, but
maybe the whole thing would be simpler if they could share the
implementation, like:

  struct ref_storage_be *find_ref_storage_backend(const char *name)
  {
	struct ref_storage *be;
	for (be = refs_backends; be; be = be->next)
		if (!strcmp(be->name, name))
			return be;
	return NULL;
  }

  int set_ref_storage_backend(const char *name)
  {
	struct ref_storage *be = find_ref_storage_backend(name);
	if (!be)
		return -1;
	the_refs_backend = be;
	return 0;
  }

You don't really need an "exists", as you can check that "find" doesn't
return NULL, but you could wrap it, of course.

-Peff