Coding standards? Recommendations?

I've noticed a variety of coding styles in the PostgreSQL source code.  In 
particular, I see a mix of naming conventions.  Some variables use camelCase 
(or CamelCase), others use under_score_style.

I'm just wondering if there's a preferred naming convention.  Is there an 
official convention?  An unofficial recommendation?  Or even a majority 
preference?

I'm not necessarily arguing for an official standard, but I'd be happy to 
follow a standard/recommendation if there is one.  I find it just as easy to 
write conforming code as non-conforming code.

(sorry if this has been covered before - if you can point me to a document 
that covers the information I'm looking for, that would be very helpful).
        -- Korry