Write lock versions back to Gemfile

lock_gemfile.rb

gemfile = File.read('Gemfile')

locks = Bundler.locked_gems
specs = locks.specs

# Naively convert to single quotes
gemfile.gsub! '"', "'"

specs.each do |gem|
  # Don't try to set versions on git or github sources
  # Don't match if version is already set
  gemfile.gsub! /^(?!.*, (git:|github:|'))( *gem '#{gem.name}')/, "\\2, '~> #{gem.version}'"
end

File.open 'Gemfile', 'w+' do |file|
  file.puts gemfile
end