How to use homepage.php instead of index.php?

[eluser]turco[/eluser]
I'd like to prepare a temporary "work in progress" homepage for my website, that will be what users will see when they'll go to www.mydomain.com
So I'm trying to find a way to redirect all CI calls not to index.php, but to homepage.php. I need that so I can continue working on my site even if it's not normally "visibile". I'd like to hide homepage.php from the URI by mod_rewrite technique. What can I do?