I released a gem-patch plugin for RubyGems. The plugin adds the patch command to RubyGems. The patch command helps to patch gems without manually opening and rebuilding them. It opens a given .gem file, extracts it, patches it with system patch command, clones its spec, updates the file list and builds the patched gem. It works on both RubyGems 1.8 and 2.0, branch for each version is also available.

Installation and usage are covered in GitHub repository. Comments are welcomed.