title: How to contribute to homebrew-cask using GitHub?
body: <p>The quotation below is the instruction to contribute to brew-cask. However, I could not understand the sentence: <code>github_user='&lt;my-github-username&gt;'</code>, I do not know whether should I input <code>&lt;&gt;</code>, and what is the <code>github_user</code>?</p>
  
  <p>There is one email address, two names for one single GitHub account. What is more, when I input the last sentence: <code>cask-repair --pull origin --push $github_user $outdated_cask</code>. There is 2 errors: <code>the requested upstream branch 'Andy1984' does not exist</code>, and </p>
  
  <pre><code>Error creating pull request: Unprocessable Entity (HTTP 422)
  Invalid value for "head"
  </code></pre>
  
  <p>and the result is <code>There was an error submitting the pull request. Have you forked the repo and made sure the pull and push remotes exist?</code> I am quite sure I followed the instructions. What is wrong?</p>
  
  <pre><code># install and setup script - only needed once
  brew install vitorgalvao/tiny-scripts/cask-repair
  cask-repair --help
  
  # fork homebrew-cask to your account - only needed once
  cd "$(brew --repository)/Library/Taps/caskroom/homebrew-cask/Casks"
  hub fork
  
  # use to update &lt;outdated_cask&gt;
  outdated_cask='&lt;the-cask-i-want-to-update&gt;'
  github_user='&lt;my-github-username&gt;'
  cd "$(brew --repository)/Library/Taps/caskroom/homebrew-cask/Casks"
  
  cask-repair --pull origin --push $github_user $outdated_cask
  </code></pre>