title: how to run a custom rake task from mina deployment script
body: <p>i am using mina for deploying my application. I specify the env(staging/production) where i want to deploy the app.</p>
  
  <pre><code>mina deploy on=staging --verbose
  </code></pre>
  
  <p>i have saved the app env in deploy.rb as</p>
  
  <pre><code>app_env = ENV['on'] || 'staging'
  </code></pre>
  
  <p>i have a rake task that takes production database backup. As of now, i run that rake task explicitly on my console as</p>
  
  <pre><code>bundle exec rake deploy:backup_prod_db --trace
  </code></pre>
  
  <p>I want to run that task on every production deployment. How do i do it?</p>