What does dirty/clean working directory mean?
<p>From Version Control with Git by Leoliger 2ed,</p>

<blockquote>
  <p>After you commit the addition of the new file into the repository, git status indicates
  that there are no outstanding, staged changes to be committed.</p>

<pre><code> $ git status
 # On branch master
 nothing to commit (working directory clean)
</code></pre>
  
  <p>Git also takes the time to tell you that <strong>your working directory is clean</strong>, which means
  the working directory has no <strong>unknown</strong> or <strong>modified</strong> files that differ from what is in the
  repository.</p>
</blockquote>

<p>Does "modified" files mean the same as tracked files that are modified but uncommitted? Does "tracked files" mean files that have been committed before?</p>

<p>What does "unknown" files mean? </p>

<p>Does ignored files not count?</p>

<p>Does untracked but not ignored files count as "unknown"?</p>

<p>Btw, in Pro Git by Chacon:</p>

<blockquote>
<pre><code>$ git status
On branch master
nothing to commit, working directory clean
</code></pre>
</blockquote>

<p>This means you have a clean working directory – in other words, there are no
<strong>tracked and modified</strong> files.</p>