title: Git search for string in a single file's history
body: <p>So if I have a file called <strong>foo.rb</strong> and it is giving me an error for a missing method called <strong>bar</strong>, so I want to search the history of <strong>foo.rb</strong> for the string <code>bar</code> to see if it was ever defined in the past.</p>
  
  <p>I found this <a href="https://stackoverflow.com/questions/4468361/search-all-of-git-history-for-string">Search all of Git history for a string?</a></p>
  
  <p>But this searches all files. I just want to search in one file.</p>