title: Not a valid object name: 'master'
body: <p>I created new directory <strong>test</strong> and <strong>CD</strong> into it<br>
  Creating new Repository into it :  </p>
  
  <pre><code>git init
  </code></pre>
  
  <p>Creating one text file <strong>test.txt</strong> and one directory with another text file inside it <strong>mydir/newfile.txt</strong> :  </p>
  
  <pre><code>echo "Hello" &gt; test.txt 
  mkdir mydir
  echo "hello" &gt; mydir/newfile.txt
  git add test.txt
  git add mydir/newfile.txt
  git commit
  </code></pre>
  
  <p>After these steps when i want to have a branch by writing :  </p>
  
  <pre><code>git branch new_branch
  </code></pre>
  
  <p>I have the error :</p>
  
  <blockquote>
    <p>fatal: Not a valid object name: 'master'</p>
  </blockquote>