title: What's this minor mode -- indicating recent change in left margin
body: <p><img src="https://i.stack.imgur.com/BV8Bu.png" alt="enter image description here">
  This is the emacs init file from <a href="https://github.com/purcell/emacs.d/" rel="nofollow noreferrer">https://github.com/purcell/emacs.d/</a>, does anyone knows what's the package make the highlight of recent changes in left margin? Thanks.</p>
  
  <p>Also, this emacs profile has a function, when the cursor stays on a word (goto-char in the figure) for around 3 seconds, all of its other occurrence in the buffer are highlighted as well. Please also let me know what's the packages achieving that.</p>
  
  <p>Appreciate the help. </p>