Re: [RFC/WIP PATCH 00/11] Protocol version 2, again!

[Duy Nguyen <pclouds@gmail.com>]

On Tue, Jun 2, 2015 at 12:49 AM, Stefan Beller <sbeller@google.com> wrote:
> However the client side with builtin/fetch, builtin/fetch-pack, fetch-pack
> is a bit of a mystery to me, as I cannot fully grasp the difference between
>  * connect.{h,c}
>  * remote.{h.c}
>  * transport.{h.c}
> there. All of it seems to be doing network related stuff, but I have trouble
> getting the big picture. I am assuming all of these 3 are rather a low level,
> used like a library, though there must be even more hierarchy in there,
> connect is most low level judging from the header file and used by
> the other two.
> transport.h seems to provide the most toplevel library stuff as it includes
> remote.h in its header?

I think transport.c is there to support non-native protocols (and
later on, smart http). So yeah it's basically the API for fetches and
pushes. git-log over those files may reveal their purposes, especially
the few first versions of them.

> The problem I am currently trying to tackle, is passing the options through all
> the layers early on. so in a few places we have code like
>
>     switch (version) {
>     case 2: /* first talk about capabilities, then get the heads */
>         get_remote_capabilities(data->fd[0], NULL, 0);
>         select_capabilities();
>         request_capabilities(data->fd[1]);
>         /* fall through */
>     case 1:
>         get_remote_heads(data->fd[0], NULL, 0, &refs,
>                  for_push ? REF_NORMAL : 0,
>                  &data->extra_have,
>                  &data->shallow);
>         break;
>     default:
>         die("BUG: Transport version %d not supported", version);
>         break;
>     }
>
> and the issue I am concerned about is the select_capabilities as well as
> the request_capabilities function here. The select_capabilities functionality
> is currently residing in the high level parts of the code as it both depends on
> the advertised server capabilities and on the user input (--use-frotz or config
> options), so the capability selection is done in fetchpack.c
>
> So there are 2 routes to go: Either we leave the select_capabilities in the
> upper layers (near the actual high level command, fetch, fetchpack) or we put
> it into the transport layer and just passing in a struct what the user desires.
> And when the users desire doesn't meet the server capabilities we die deep down
> in the transport layer.

I read the latest re-roll and I think the placement makes sense. You
can't put protocol specific at transport level because "pack protocol"
is just one of the supported protocols. There is smart-http (which
shares a bunch of code, but from transport perspective is a separate
protocol), and then user-defined protocols that know nothing about
this v2.
-- 
Duy