title: vim fold text with spaces in front
body: <p>I'm trying to customize vim folding style and stuck with indentation. I know it has been asked multiple times here and I use this command (which seem to work for others) to test the appearance of fold:</p>
  
  <pre><code>:set foldtext=' '.foldtext()
  </code></pre>
  
  <p>This however gives me 'unknown option' error. Apparently, it doesn't accept the string containing only space(s), because this</p>
  
  <pre><code>:set foldtext='mytext'.foldtext()
  </code></pre>
  
  <p>works fine and adds 'mytext' to the beginning of folds.</p>
  
  <p>Why doesn't it work and what's the way around it?</p>