There are good points here, but it's possible to take a more sophisticated approach to these things. You don't have to leave configs out entirely just to avoid

There are good points here, but it's possible to take a more sophisticated approach to these things. You don't have to leave configs out entirely just to avoid putting passwords in the repo. Just don't put passwords in the repo. Also, checking in CSS files compiled from Sass (for example) can be a pragmatic way around the dilemma of having to deploy a separate Ruby stack, or have a more complicated build process (small projects only). I've actually never worked in a place that didn't check in images. Where would they go?