title: How to completely replace one file in GIt
body: <p>All:</p>
  
  <p>I am pretty new in Git, I wonder how can I replace one file with the one from master?</p>
  
  <p>Foe example:</p>
  
  <p>In branch DEV, I have one file called App.js, I decide to use the App.js from master branch to replace it. What is the command to do this?</p>
  
  <p>Thanks</p>