Re: [PATCH v2 08/11] fetch-pack: advertise trace2 SID in capabilities

> When trace2 is enabled, the server sent a trace2-sid capability, and
> trace2.advertiseSID is true, advertise fetch-pack's own session ID back
> to the server.
>
> Signed-off-by: Josh Steadmon <steadmon@google.com>
> ---
>  fetch-pack.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/fetch-pack.c b/fetch-pack.c
> index b10c432315..7fbefa7b8e 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -35,6 +35,8 @@ static int fetch_fsck_objects = -1;
>  static int transfer_fsck_objects = -1;
>  static int agent_supported;
>  static int server_supports_filtering;
> +static int server_sent_trace2_sid;
> +static int advertise_trace2_sid;
>  static struct shallow_lock shallow_lock;
>  static const char *alternate_shallow_file;
>  static struct strbuf fsck_msg_types = STRBUF_INIT;
> @@ -326,6 +328,8 @@ static int find_common(struct fetch_negotiator *negotiator,
>  			if (deepen_not_ok)      strbuf_addstr(&c, " deepen-not");
>  			if (agent_supported)    strbuf_addf(&c, " agent=%s",
>  							    git_user_agent_sanitized());
> +			if (advertise_trace2_sid && server_sent_trace2_sid && trace2_is_enabled())
> +				strbuf_addf(&c, " trace2-sid=%s", trace2_session_id());
>  			if (args->filter_options.choice)
>  				strbuf_addstr(&c, " filter");
>  			packet_buf_write(&req_buf, "want %s%s\n", remote_hex, c.buf);
> @@ -979,6 +983,9 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args,
>  				      agent_len, agent_feature);
>  	}
>  
> +	if (server_supports("trace2-sid"))
> +		server_sent_trace2_sid = 1;
> +
>  	if (server_supports("shallow"))
>  		print_verbose(args, _("Server supports %s"), "shallow");
>  	else if (args->depth > 0 || is_repository_shallow(r))
> @@ -1191,6 +1198,8 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
>  		packet_buf_write(&req_buf, "command=fetch");
>  	if (server_supports_v2("agent", 0))
>  		packet_buf_write(&req_buf, "agent=%s", git_user_agent_sanitized());
> +	if (advertise_trace2_sid && server_supports_v2("trace2-sid", 0) && trace2_is_enabled())
> +		packet_buf_write(&req_buf, "trace2-sid=%s", trace2_session_id());
>  	if (args->server_options && args->server_options->nr &&
>  	    server_supports_v2("server-option", 1)) {
>  		int i;
> @@ -1711,6 +1720,7 @@ static void fetch_pack_config(void)
>  	git_config_get_bool("repack.usedeltabaseoffset", &prefer_ofs_delta);
>  	git_config_get_bool("fetch.fsckobjects", &fetch_fsck_objects);
>  	git_config_get_bool("transfer.fsckobjects", &transfer_fsck_objects);
> +	git_config_get_bool("trace2.advertisesid", &advertise_trace2_sid);
>  	if (!uri_protocols.nr) {
>  		char *str;