title: How to add subfolder to gitignore file?
body: <p>I have .gitignore in learning_python folder,</p>
  
  <p>need to add .ipynb_checkpoints folder to .gitignore.</p>
  
  <p>.ipynb folder location:</p>
  
  <pre><code>learning_python/python_crash_course/.ipynb_checkpoints/
  </code></pre>