Clarifying the Roles of the .gemspec and Gemfile « Katz Got Your Tongue?

The roles of the gem spec and gemfile

For the reasons described above, it can sometimes be useful for application developers to declare a dependency on a gem which has not yet been released. When bundler fetches that gem, it uses the .gemspec file found in the git repository’s root to extract its metadata as well as discover additional dependencies declared by the in-development gem. This means that git gems can seamlessly be used by bundler, because their .gemspec allows them to look exactly like normal gems (including, importantly, having more dependencies of its own). The only difference is that the application developer has told bundler exactly where to look for the gem in question.

Full article: http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-...