module Rails::Command::EnvironmentArgument

def acceptable_environment(env = nil)
  if available_environments.include? env
    env
  else
    %w( production development test ).detect { |e| /^#{env}/.match?(e) } || env
  end
end

def available_environments
  Dir["config/environments/*.rb"].map { |fname| File.basename(fname, ".*") }
end

def extract_environment_option_from_argument(default_environment: Rails::Command.environment)
  if options[:environment]
    self.options = options.merge(environment: acceptable_environment(options[:environment]))
  else
    self.options = options.merge(environment: default_environment)
  end
end