title: Remove spurious second root in a git repo
body: <p>Somehow we have 2 roots in a git repo. One is what we expect, master and other branches. The other is a completely unrelated repo.</p>
  
  <p>So, if I do <code>git checkout master</code>, I get what we expect. I've found the last commit hash for the odd root, and if I <code>git checkout ca992b28a</code> (for a headless checkout), I get this other random repo.</p>
  
  <p>How do I remove it?
  How do I find who committed it?
  The commit is part of the <a href="https://github.com/thephpleague/omnipay-sagepay" rel="nofollow noreferrer">https://github.com/thephpleague/omnipay-sagepay</a> repo that a couple of my colleagues work on, but this is completely unrelated to the repo in question.</p>
  
  <p>The commit points to a commit in 2016.
  The presence of the commit in our repo is in the last 30 days.</p>
  
  <p><a href="https://i.stack.imgur.com/dzwRh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dzwRh.png" alt="Sourcetree view of foreign root"></a></p>