title: CocoaPods: point to a branch in pod spec
body: <p>I'm trying to install code from a repository's branch on a pod spec, and based on the documentation, this should work:</p>
  
  <pre><code>s.dependency 'repository_name',
  :git =&gt; 'https://github.com/account_name/repository_name.git',
  :branch =&gt; 'experimental_branch'
  </code></pre>
  
  <p>But I get an error with something like <strong>[!] Unsupported version requirements. Updating CocoaPods might fix the issue.</strong></p>
  
  <p>It works when installing from a pod file directly:</p>
  
  <pre><code>pod 'ObjectiveRecord', :git =&gt; 'https://github.com/supermarin/ObjectiveRecord.git', :branch =&gt; '2-0-experimental'
  </code></pre>
  
  <p>Does anyone know? Thanks!</p>