when you have secret key in your project, how can pushing to GitHub be possible?

I am trying to push a brand new, empty Rail 3.0.4 project to GitHub, but just realize that the cookie session store has a secret key:

In config/initializers/secret_token.rb

NewRuby192Rails304Proj::Application.config.secret_token = '22e8...'

So how can we avoid it being push to GitHub? We can ignore this file (using .gitignore), but without this file, a Rails app won't run at all (and is not a complete Rails app). Or in general, other files or frameworks may have files containing secret keys too. In such case, how should it be handled when pushing to GitHub?