class Bundler::EnvironmentPreserver

def backup
  env = restore.clone
  @keys.each do |key|
    value = env[key]
    env[@prefix + key] = value unless value.nil? || value.empty?
  end
  env
end

def initialize(env, keys)
  @original = env.to_hash
  @keys = keys
  @prefix = "BUNDLE_ORIG_"
end

def restore
  env = @original.clone
  @keys.each do |key|
    value_original = env[@prefix + key]
    unless value_original.nil? || value_original.empty?
      env[key] = value_original
      env.delete(@prefix + key)
    end
  end
  env
end