title: `fatal: Not a valid object name: 'master'` when creating a new branch in git
body: <p>I followed <a href="https://www.atlassian.com/git/tutorial/git-basics#!add" rel="noreferrer">this tutorial</a> but I'm having trouble creating a new branch in a new repository. This is the error I'm getting:</p>
  
  <p><img src="https://i.stack.imgur.com/mySA5.jpg" alt="enter image description here"></p>
  
  <p>What am I doing wrong?</p>