class Gem::Commands::FetchCommand

def execute
  version = options[:version] || Gem::Requirement.default
  platform  = Gem.platforms.last
  gem_names = get_all_gem_names
  gem_names.each do |gem_name|
    dep = Gem::Dependency.new gem_name, version
    dep.prerelease = options[:prerelease]
    specs_and_sources, errors =
      Gem::SpecFetcher.fetcher.spec_for_dependency dep
    if platform
      filtered = specs_and_sources.select {|s,| s.platform == platform }
      specs_and_sources = filtered unless filtered.empty?
    end
    spec, source = specs_and_sources.max_by {|s,| s.version }
    if spec.nil?
      show_lookup_failure gem_name, version, errors, options[:domain]
      next
    end
    source.download spec
    say "Downloaded #{spec.full_name}"
  end
end