This is a issue fix quite often.. and its really annoying to get it right.
So… I am giving it a try to solve it once and for all, at least for myself.
Whenever I install a Mac for myself, I always use MacPorts (http://www.macports.com) for futher software (such as apache, ant, php ect). So I also use it for bash completion. The thing though is that the bash completion from MacPorts comes without any completions, or so it seems. So how do we get them working? Well… lets take it from the top.