.ssh/rc to constant ssh_auth_sock but not fake X11 auth

sshrc

if test "$SSH_AUTH_SOCK" ; then
    ln -sf $SSH_AUTH_SOCK ~/.ssh/ssh_auth_sock
    SSH_AUTH_SOCK=~/.ssh/ssh_auth_sock
    export SSH_AUTH_SOCK
fi

# example sshrc file
if read proto cookie && [ -n "$DISPLAY" ]; then
     if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then
	     # X11UseLocalhost=yes
	     echo add unix:`echo $DISPLAY | cut -c11-` $proto $cookie
     else
	     # X11UseLocalhost=no
	     echo add $DISPLAY $proto $cookie
     fi | xauth -q -
fi