title: How do you rollback to a previous Gemfile.Lock?
body: <p>I recently ran 'bundle update,' and it updated the Twitter-bootstrap-rails gem to the latest version. Ever since then, the header size has changed, and I would like to roll back to the previous gem versions for all my gems.</p>
  
  <p>I tried rolling back to my previous gemfile and bundle updating, but the problem was I didn't specify versions in my gemfile so it doesn't know to degrade a version. I also tried checking the specific previous version and specifying that, but I think all the dependencies changed as well.</p>
  
  <p>So I need to find a way to just go back to using all the old versions, which seems to be stored in the Gemfile.lock file. How would I do this?</p>