It used to be that every project had its own .ruby_version file. But you’d also have to specify the same version in the Gemfile. I say nay to .ruby_version and instead get it from one place:

alias ruby-vers="cat Gemfile | grep '^ruby' | sed -E \"s/.*[\\\"'](.+)[\\\"']/\1/"\"

Now you can $ chruby `ruby-vers` your way to success!