Windows: work around hanging send-pack (aka push over git protocol)
On Windows, git suffers from a hang in send-pack that is to be attributed
to the following conditions:
- A thread is spawned (the sideband demultiplexer).
- The thread reads from a network socket.
- The network socket is also inherited to a child process (pack-objects).
With this combination of conditions, we observe a hang in send-pack that
so far nobody has been able to explain, let alone to fix properly.
With this patch we work around the problem by not using the sideband on
Windows at all in send-pack.
Signed-off-by: Johannes Sixt <j6t@kdbg.org>