Buffering in mercurial with redirected output

[Sergey Antonov]

I'm using a mercurial command line client with redirected output to make 
a GUI around some of mercurial commands.

The problem I have is that the output is buffered and I don't get any 
output from the command until it ends or until there is more output then 
the buffer length.

For example, when I use it for commands: incoming, outgoing, pull, push, 
I would like to show every line as soon as it is available.

Is there a way to disable buffering of redirected output or enable flush 
after each newline ?

-- 
Sergey Antonov
sergant_ at mail.ru