title: C command-line parser for handling comments
body: <p>I have a <code>tool</code> that takes <code>input</code> and makes <code>output</code>:</p>
  
  <pre><code>$ tool input &gt; output
  </code></pre>
  
  <p>I'd like to add an option that is a long string — say, a "comment" option. This comment text is an argument to the option and is a sentence enclosed in forward tick marks:</p>
  
  <pre><code>$ tool --comment='I am commenting on the use of comments' input &gt; output_plus_comment
  </code></pre>
  
  <p>This is different from the usual <code>--foo=bar</code> key-value pairing, where <code>foo</code> is the option name and <code>bar</code> is a one-word value (e.g., <code>true</code>, <code>red</code>, ...).</p>
  
  <p>Is there a good command-line parser library for C that handles this particular case?</p>