Teach screen and tmux about the current ssh-agent configuration

mp_wrap.sh

function multiplex_terminal() {
  cp /dev/null $HOME/.sshvars
  chmod 600 $HOME/.sshvars
  for i in SSH_CLIENT SSH_TTY SSH_AUTH_SOCK SSH_CONNECTION
  do
    eval v="\$$i"
    echo export $i=\"$v\" >> $HOME/.sshvars
  done
  multiplexor_path="`/usr/bin/which ${1}`"
  shift
  export IN_MULTIPLEXOR=yes
  $multiplexor_path $*
  rm -f $HOME/.sshvars
}

function ssh_connect() {
  (
    [ -n "$IN_MULTIPLEXOR" -a -f $HOME/.sshvars ] && . $HOME/.sshvars
    ssh_path="`/usr/bin/which ${1}`"
    shift
    exec $ssh_path $*
  )
}

alias tmux="multiplex_terminal tmux"
alias screen="multiplex_terminal screen"
alias ssh="ssh_connect ssh"
alias scp="ssh_connect scp"
alias sftp="ssh_connect sftp"