Force reading with SSH_ASKPASS?

[Phil]

Hi,

I'm looking at integrating sftp into a larger project. It would be nice if 
there was a way to force read_passphrase() (in readpass.c) to use SSH_ASKPASS 
regardless of the properties of the terminal. 

This would be easy enough to do, an environment variable or a new flag 
definition would achieve this (I'm using an environment variable for 
convenience at the moment). Would anyone be interested in receiving a patch 
for this? If so, which apporach would you prefer?

Thanks,
 -phil