Subject: Re: [PATCH v2 1/2] transport: warn if server options are unsupported

From: Jonathan Nieder <[email-masked]>
Date: Tue, 9 Apr 2019 13:45:25 -0700

Hi,

Jonathan Tan wrote:

> Server options were added in commit 5e3548ef16 ("fetch: send server
> options when using protocol v2", 2018-04-24), supported only for
> protocol version 2. Add a warning if server options are specified for
> the user if a legacy protocol is used instead.
>
> An effort is made to avoid printing the same warning more than once by
> clearing transport->server_options after the warning, but this does not
> fully avoid double-printing (for example, when backfulling tags using
> another fetch with a non-reusable transport).
>
> Signed-off-by: Jonathan Tan <[email-masked]>
> ---
>  t/t5702-protocol-v2.sh | 17 +++++++++++++++++
>  transport.c            |  8 ++++++++
>  2 files changed, 25 insertions(+)

Thanks for writing this.  I'd be in favor of making this die().
Compare what we already do in push:

	if (args->push_options && !push_options_supported)
		die(_("the receiving end does not support push options"));

What happens in the case of push with protocol v0, where server options
are supported?

[...]
> --- a/transport.c
> +++ b/transport.c
> @@ -252,6 +252,12 @@ static int connect_setup(struct transport *transport, int for_push)
>  	return 0;
>  }
>  
> +static void warn_server_options_unsupported(struct transport *transport)
> +{
> +	warning(_("Ignoring server options because protocol version does not support it"));

nits:
- error and warning messages tend to use lowercase
- the user running into this may want to know how to switch to a better
  protocol version.  Is there e.g. a manpage we can point them to?

For example:

	fatal: server options require protocol version 2 or later
	hint: see protocol.version in "git help config" for more details

> +	transport->server_options = NULL;

Should this use a static to also warn only once in the tag-catchup case
you mentioned?

> +}
> +
>  /*
>   * Obtains the protocol version from the transport and writes it to
>   * transport->data->version, first connecting if not already connected.
> @@ -286,6 +292,7 @@ static struct ref *handshake(struct transport *transport, int for_push,
>  		break;
>  	case protocol_v1:
>  	case protocol_v0:
> +		warn_server_options_unsupported(transport);
>  		get_remote_heads(&reader, &refs,
>  				 for_push ? REF_NORMAL : 0,
>  				 &data->extra_have,
> @@ -363,6 +370,7 @@ static int fetch_refs_via_pack(struct transport *transport,
>  		break;
>  	case protocol_v1:
>  	case protocol_v0:
> +		warn_server_options_unsupported(transport);
>  		refs = fetch_pack(&args, data->fd, data->conn,

Looks like this only affects fetch, so the question above about push
is only about the commit message.

With whatever subset of the suggested changes makes sense,
Reviewed-by: Jonathan Nieder <[email-masked]>

Thanks.