send-pack: send push options correctly in stateless-rpc case

"git send-pack --stateless-rpc" puts each request in a sequence of pkt-lines
followed by a flush-pkt. The push option code forgot about this and sends push
options and their terminating delimiter as ordinary pkt-lines that get their
length header stripped off by remote-curl before being sent to the server.

The result is multiple malformed requests, which the server rejects.

Fortunately send-pack --stateless-rpc already is aware of this "pkt-line within
pkt-line" framing for the update commands that precede push options. Handle
push options the same way.

Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

send-pack.c

@@ -514,6 +514,14 @@ int send_pack(struct send_pack_args *args,
 		}
 	}
 
+	if (use_push_options) {
+		struct string_list_item *item;
+
+		packet_buf_flush(&req_buf);
+		for_each_string_list_item(item, args->push_options)
+			packet_buf_write(&req_buf, "%s", item->string);
+	}
+
 	if (args->stateless_rpc) {
 		if (!args->dry_run && (cmds_sent || is_repository_shallow())) {
 			packet_buf_flush(&req_buf);
@@ -526,18 +534,6 @@ int send_pack(struct send_pack_args *args,
 	strbuf_release(&req_buf);
 	strbuf_release(&cap_buf);
 
-	if (use_push_options) {
-		struct string_list_item *item;
-		struct strbuf sb = STRBUF_INIT;
-
-		for_each_string_list_item(item, args->push_options)
-			packet_buf_write(&sb, "%s", item->string);
-
-		write_or_die(out, sb.buf, sb.len);
-		packet_flush(out);
-		strbuf_release(&sb);
-	}
-
 	if (use_sideband && cmds_sent) {
 		memset(&demux, 0, sizeof(demux));
 		demux.proc = sideband_demux;