TODO item for pg_ctl and server detection

While I am working on pg_ctl, I saw this TODO item:
Have the postmaster write a random number to a file on startup thatpg_ctl checks against the contents of a pg_ping
responseon its initialconnection (without login)    This will protect against connecting to an old instance of
thepostmasterin a different or deleted subdirectory. 
 

http://archives.postgresql.org/pgsql-bugs/2009-10/msg00110.phphttp://archives.postgresql.org/pgsql-bugs/2009-10/msg00156.php

Based on our new PQPing(), do we ever want to implement this or should I
remove the TODO item?  It seems this would require a server connection,
which is something we didn't want to force pg_ctl -w to do in case
authentication is broken.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +