wrap a r/w stream in this transport r/w stream for transforming writes into valid git packet lines, and reads from git packet lines into JS objects.
var net =transport =clienttcptcp = netclient =client// start a fetchclient
wrap any readable/writable stream with git-packet-line senders and receivers.
enter or exit "raw" mode -- this makes writes skip the pkt-write portion of the stream and go directly to the connection.
this is useful for, e.g., sending packfile data.