how to setup ssh-agent so there is only one process running.

ssh-agent-singleton-bashrc.sh

# ssh-agent singleton setup
# If no SSH agent is already running, start one now. Re-use sockets so we never
# have to start more than one session.
export SSH_AUTH_SOCK=$HOME/.ssh-socket
NKEYS_SSHAGENT=`ssh-add -l 2> /dev/null | wc -l`
if [ $NKEYS_SSHAGENT = 0 ]; then
  # No ssh-agent running
  rm -f $SSH_AUTH_SOCK
  ssh-agent -a $SSH_AUTH_SOCK >/tmp/.ssh-script
  source /tmp/.ssh-script
  echo $SSH_AGENT_PID > $HOME/.ssh-agent-pid
  rm -f /tmp/.ssh-script
  ssh-add $HOME/.ssh/id_rsa
fi

# most of this is from here: http://www.electricmonk.nl/log/2012/04/24/re-use-existing-ssh-agent-cygwin-et-al/
# with some modifications to make it work in my environment and to add my key automagically..