class Gem::Source::Local

def find_gem gem_name, version = Gem::Requirement.default, # :nodoc:
             prerelease = false
  load_specs :complete
  found = []
  @specs.each do |n, data|
    if n.name == gem_name
      s = data[1].spec
      if version.satisfied_by?(s.version)
        if prerelease
          found << s
        elsif !s.version.prerelease?
          found << s
        end
      end
    end
  end
  found.max_by { |s| s.version }
end