title: How do I find the default branch for a repository using the Github v3 API
body: <p>My goal is to get the tree for the latest SHA in the default branch</p>
  
  <pre><code>GET /repos/:owner/:repo/git/trees/:sha
  </code></pre>
  
  <p>How do I find the lastest SHA from the default branch?</p>
  
  <p>I know that I can call</p>
  
  <pre><code>GET /repos/:owner/:repo/branches/:branch
  </code></pre>
  
  <p>But I can't just use "master" for the branch as not all repos use master as the default branch.</p>
  
  <p>How do I find out what the default branch for a repo is?</p>