Downloads all the gems from a Gemfile.lock. Inspired by https://gist.github.com/flavio/1722530

gem_downloader.rb

require 'rubygems'
require 'bundler'
require 'fileutils'

TMP_DIR = "/tmp/gems"

#If directory exists, delete it and recreates.
FileUtils.rm_rf(TMP_DIR) if File.exists?(TMP_DIR)
FileUtils.mkdir TMP_DIR

#read the Gemfile.lock
lockfile = Bundler::LockfileParser.new(Bundler.read_file("Gemfile.lock"))

#Download gems
lockfile.specs.each do |spec|
puts "Downloading gem #{spec.name}-#{spec.version}"
    Dir.chdir TMP_DIR do
    cmd =  "gem fetch #{spec.name} -v #{spec.version}"
      if !system(cmd)
        warn "Error while downloading gem #{spec.name}-#{spec.version}"
      end
    end
end