由于使用了 UPYUN 做资源存储，替换资源方便不少，在 production.rb 中已经进行了如下设置：

config.action_controller.asset_host = Settings.upyun_url

但每次发布后，都需要重新 FTP 发布资源，在寻求自动化方法的路上，我找到了 gem 'rails-assets-for-upyun', '>= 0.0.9'，可以用命令上传方便多了，但仍然没有解决自动化部署，于是考虑在 mina 的 deploy.rb 中写一段自动部署脚本，于是就解决了。

# => Deploy task
# ===========================================================================================
desc "Deploys the current version to the server."
task :deploy => :environment do
  deploy do
    # Put things that will set up an empty directory into a fully set-up
    # instance of your project.
    invoke :'git:clone'
    invoke :'deploy:link_shared_paths'
    invoke :'bundle:install'
    invoke :'rails:db_migrate'
    invoke :'rails:assets_precompile'
    invoke :'rails:assets_publish_assets_upyun'
    invoke :'deploy:cleanup'

    to :launch do
      invoke :'unicorn:restart'
    end
  end
end

namespace :rails do
  set :publish_upyun, %{
    cd #{app_path}
    bundle exec rake assets:publish_assets_upyun RAILS_ENV=production
  }
  task :assets_publish_assets_upyun do
    queue 'echo "-----> Assets To UPYUN"'
    queue! publish_upyun
  end
end

Rakefile

...
namespace :assets do
  task :publish_assets_upyun do
    RailsAssetsForUpyun.publish 'bucket', 'username', 'password'
  end
end