transport: don't flush when disconnecting stateless-rpc helper

Since ba22785 (Reduce the number of connects when fetching,
2008-02-04), when we disconnect a git transport, we send a final flush
packet. This cleanly tells the other side that we're done, and avoids
the other side complaining "the remote end hung up unexpectedly" (though
we'd only see that for transports that pass along the server stderr,
like ssh or local-host).

But when we've initiated a v2 stateless-connect session over a transport
helper, there's no point in sending this flush packet. Each operation
we've performed is self-contained, and the other side is fine with us
hanging up between operations.

But much worse, by sending the flush packet we may cause the helper to
issue an entirely new request _just_ to send the flush packet. So we can
incur an extra network request just to say "by the way, we have nothing
more to send".

Let's drop this extra flush packet. As the test shows, this reduces the
number of POSTs required for a v2 ls-remote over http from 2 to 1.

Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

t/t5702-protocol-v2.sh

@@ -652,6 +652,18 @@ test_expect_success 'fetch from namespaced repo respects namespaces' '
 	test_cmp expect actual
 '
 
+test_expect_success 'ls-remote with v2 http sends only one POST' '
+	test_when_finished "rm -f log" &&
+
+	git ls-remote "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" >expect &&
+	GIT_TRACE_CURL="$(pwd)/log" git -c protocol.version=2 \
+		ls-remote "$HTTPD_URL/smart/http_parent" >actual &&
+	test_cmp expect actual &&
+
+	grep "Send header: POST" log >posts &&
+	test_line_count = 1 posts
+'
+
 test_expect_success 'push with http:// and a config of v2 does not request v2' '
 	test_when_finished "rm -f log" &&
 	# Till v2 for push is designed, make sure that if a client has

transport.c

@@ -730,7 +730,7 @@ static int disconnect_git(struct transport *transport)
 {
 	struct git_transport_data *data = transport->data;
 	if (data->conn) {
-		if (data->got_remote_heads)
+		if (data->got_remote_heads && !transport->stateless_rpc)
 			packet_flush(data->fd[1]);
 		close(data->fd[0]);
 		close(data->fd[1]);