title: does git add only add untracked files or modified files to the staging area?
body: <p>I'm new to Git, let's say I create 10 files in once, then I added those 10 files to stage area, then committed them.</p>
  
  <p>And then I created another file(11th file), because this file's name is very long, I don't want to type git command like</p>
  
  <blockquote>
    <p>git add lllllllllllllongname.txt</p>
  </blockquote>
  
  <p>instead, I typed:</p>
  
  <blockquote>
    <p>git add .</p>
  </blockquote>
  
  <p>Does git also re-add those 10 files created on the first time to the staging area again internally?
  becuase I checked Git docs, it doesn't say <code>add</code> command will only add untracked files or modified files to the staging area?</p>