gemdiff is a command-line tool to find source code for ruby gems. You can
compare source code differences between the current version of a gem in your
bundle and the version of the gem that would be installed with bundle update
<gem> (or any two versions of a gem). gemdiff connects gem version management
(rubygems + bundler) with source code (GitHub).

WWW: https://github.com/teeparham/gemdiff