asciinema.org/config/initializers/carrierwave.rb

CarrierWave.configure do |config|
  if CFG.s3_bucket
    config.storage = :fog
    config.fog_directory = CFG.s3_bucket
    config.fog_public = false

    config.fog_credentials = {
      provider: 'AWS',
      aws_access_key_id: CFG.aws_access_key_id,
      aws_secret_access_key: CFG.aws_secret_access_key,
      region: CFG.s3_region
    }
  else
    config.root = Rails.root
  end
end

if File.exists?(Rails.root.to_s + "/public/uploads/asciicast")
  raise "Please move all directories from ./public/uploads/ to ./uploads/"
end

# fix filename (remove ?AWSAccessKeyId=...)
CarrierWave::Storage::Fog::File.class_eval do
  def filename(options = {})
    if file_url = url(options)
      file_url.gsub(/.*\/(.*?$)/, '\1').sub(/\?.*$/, '')
    end
  end
end