add version approximation strings to Gemfile

gistfile1.rb

out = ''
File.readlines('./Gemfile').each do |line|
  match = line.match(/^(.*)gem '([^']+)'(, require: false)?$/)
  if match
    name = match[2]
    version = Gem.loaded_specs[name].version
    ver_str = version.to_s
    if ver_str.start_with?('0.')
      ver_str = ver_str.sub(/\.\d+$/, '.x')
      spec = "~> #{ver_str}"
    else
      spec = version.approximate_recommendation
    end

    out << "#{match[1]}gem '#{name}', '#{spec}'#{match[3]}\n"

  else
    out << line
  end
end; 0

File.open('./Gemfile', 'w') {|f| f.write(out) }