mvz/alexandria-book-collection-manager — comment on commit d689dc1f7d896d0f37a02ba7c6be6708bb760ced
File:  line 0
By mvz:

Keeping Gemfile.lock under version control is good practice if your development and production environments are all basically the same, e.g., when developing a Rails app as a team for deployment to a known server.

For software that will be developed and deployed on a very diverse set of environments, such as gems, ignoring Gemfile.lock is the best option. I believe Alexandria falls under that category.