HISTFILE and MAXHISTSIZE warnings for Mongrel/Rails on OS X Leopard

http://discuss.joyent.com/viewtopic.php?pid=153325

Ever since I’ve upgraded by 12” PowerBook G4 (yes, I know) to Leopard, I’ve been getting the following error:

/etc/irbrc:14: warning: already initialized constant HISTFILE/etc/irbrc:15: warning: already initialized constant MAXHISTSIZE

Here’s a fix. =)