I have a problem with a rails app that I thought would have been fixed by switching from the mysql gem to the ruby-mysql gem. Unfortunately, after deploying this change, the entire app crashed. And due to my unfamiliarity with git, I screwed that up as well. Here is how I fixed things:
yo$ rm -rf .bundle && bundle install && git add Gemfile.lock && git commit -m "Added Gemfile.lock" yo$ git push --all yo$ cap deploy