title: How to get a specific "commit" of a gem from github?
body: <p>I'm using <a href="https://github.com/sferik/rails_admin" rel="noreferrer">rails_admin</a>, and since it is in (very) active development, bugs turn up every now and then.</p>
  
  <p>There are no versions for the gem as far as I can tell, for the gem in github, so I can't use the <code>:version</code> key for the gem declaration in the Gemfile .</p>
  
  <p>Is there a way I can "tie" a specific commit(that I know is working fine for me) to the Gemfile ?</p>
  
  <p>I currently have in my Gemfile:</p>
  
  <pre><code>gem 'rails_admin', 
    :git =&gt; 'git://github.com/sferik/rails_admin.git'
  </code></pre>
  
  <p>I'd like to be able to do something like this (example "commit_id"):</p>
  
  <pre><code>gem 'rails_admin', 
    :git =&gt; 'git://github.com/sferik/rails_admin.git',
    :commit_id =&gt; "4e7d53e3c5c4c3c5c43c3"
  </code></pre>
  
  <p>Is this possible to do with github?</p>