scope path: :uploads do
  # Note attachments and User/Group/Project/Topic avatars
  get "-/system/:model/:mounted_as/:id/:filename",
  to: "uploads#show",
  constraints: { model: %r{note|user|group|project|projects\/topic|achievements\/achievement}, mounted_as: /avatar|attachment/, filename: %r{[^/]+} }
......

# This should either
#   - send the file directly
#   - or redirect to its URL
#
def show
  return render_404 unless uploader&.exists?

  ttl, directives = *cache_settings
  ttl ||= 0
  directives ||= { private: true, must_revalidate: true }

  expires_in ttl, directives

  file_uploader = [uploader, *uploader.versions.values].find do |version|
    version.filename == params[:filename]
  end

  return render_404 unless file_uploader

  workhorse_set_content_type!
  send_upload(file_uploader, attachment: file_uploader.filename, disposition: content_disposition)
end

def send_upload(file_upload, send_params: {}, redirect_params: {}, attachment: nil, proxy: false, disposition: 'attachment')
  content_type = content_type_for(attachment)

  if attachment
    response_disposition = ActionDispatch::Http::ContentDisposition.format(disposition: disposition, filename: attachment)

    # Response-Content-Type will not override an existing Content-Type in
    # Google Cloud Storage, so the metadata needs to be cleared on GCS for
    # this to work. However, this override works with AWS.
    redirect_params[:query] = { "response-content-disposition" => response_disposition,
                                "response-content-type" => content_type }
    # By default, Rails will send uploads with an extension of .js with a
    # content-type of text/javascript, which will trigger Rails'
    # cross-origin JavaScript protection.
    send_params[:content_type] = 'text/plain' if File.extname(attachment) == '.js'

    send_params.merge!(filename: attachment, disposition: disposition)
  end

  if image_scaling_request?(file_upload)
    location = file_upload.file_storage? ? file_upload.path : file_upload.url
    headers.store(*Gitlab::Workhorse.send_scaled_image(location, params[:width].to_i, content_type))
    head :ok
  elsif file_upload.file_storage?
    send_file file_upload.path, send_params
  elsif file_upload.class.proxy_download_enabled? || proxy
    headers.store(*Gitlab::Workhorse.send_url(file_upload.url(**redirect_params)))
    head :ok
  else
    redirect_to cdn_fronted_url(file_upload, redirect_params)
  end
end