rewrite POST into GET?

[Mark Slater]

I'm working on a facebook application built using Rails. This is my  
first time deploying a Rails site, and I'm setting up Capistrano to do  
the heavy lifting. I've got it creating a "down for maintenance" file  
that I would like served to all facebook requests when I'm updating  
things, but facebook always sends a POST request. This causes Nginx to  
respond with a 405 and report "client sent invalid method...";  
obviously you can't really POST to a static page.

Is there a way I can re-direct POST requests to GET requests or force  
Nginx to return the static page regardless of the method used to  
access it? My backup plan is to deploy a second app on a different set  
of ports that always returns the "down for maintenance" message....  
but it seems silly to run one app to report you're upgrading another.

Thanks!

Mark