Re: [PATCHv3 1/6] receive-pack.c: add protocol support to negotiate atomic

[Eric Sunshine <sunshine@sunshineco.com>]

On Wed, Dec 17, 2014 at 1:32 PM, Stefan Beller <sbeller@google.com> wrote:
> From: Ronnie Sahlberg <sahlberg@google.com>
>
> This adds support to the protocol between send-pack and receive-pack to
> * allow receive-pack to inform the client that it has atomic push capability
> * allow send-pack to request atomic push back.
>
> There is currently no setting in send-pack to actually request that atomic
> pushes are to be used yet. This only adds protocol capability not ability
> for the user to activate it.
>
> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
> diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt
> index 6d5424c..68ec23d 100644
> --- a/Documentation/technical/protocol-capabilities.txt
> +++ b/Documentation/technical/protocol-capabilities.txt
> @@ -244,6 +245,14 @@ respond with the 'quiet' capability to suppress server-side progress
>  reporting if the local progress reporting is also being suppressed
>  (e.g., via `push -q`, or if stderr does not go to a tty).
>
> +atomic
> +------
> +
> +If the server sends the 'atomic' capability it is capable of accepting
> +atomic pushes. If the pushing client requests this capability, the server
> +will update the refs in one single atomic transaction. Either all refs are

"one single atomic" sounds awfully redundant.

> +updated or none.
> +
>  allow-tip-sha1-in-want
>  ----------------------
>
> diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
> index 32fc540..e76e5d5 100644
> --- a/builtin/receive-pack.c
> +++ b/builtin/receive-pack.c
> @@ -328,6 +332,10 @@ int send_pack(struct send_pack_args *args,
>                         "Perhaps you should specify a branch such as 'master'.\n");
>                 return 0;
>         }
> +       if (args->atomic && !atomic_supported) {
> +               return error("server does not support atomic push.");

Just above this code, the 'args->push_cert' check uses die() rather
than error() when the remote side fails to support the requested
feature.

> +       }
> +       use_atomic = atomic_supported && args->atomic;
>
>         if (status_report)
>                 strbuf_addstr(&cap_buf, " report-status");