title: remove a file from working directory and them commit compared to use git rm
body: <p>I'm reading a Git book, it says:</p>
  
  <p><strong>To remove a file from Git, you have to remove it from your tracked files (more accurately, remove it from your staging area) and then commit. The "git rm" command does that</strong></p>
  
  <p>but I think I can also achieve the same thing in this way, let's say I need to remove a text file called <code>abc.txt</code>:
  Firstly, I delete the <code>abc.txt</code>.
  Secondly, I use:</p>
  
  <blockquote>
    <p>git add abc.txt</p>
  </blockquote>
  
  <p>and then</p>
  
  <blockquote>
    <p>git commit -m "remove abc.txt"</p>
  </blockquote>
  
  <p>isn't that the same thing as use <code>git rm</code>?</p>
  
  <p>Another question I have is, I have manually deleted <code>abc.txt</code>, so it doesn't exist on the hard disk anymore, how still I can issue "git add abc.txt" as the file still exist?</p>