title: What's the Kingfisher default cache behavior?
body: <p>I am using <a href="https://github.com/onevcat/Kingfisher" rel="nofollow noreferrer">Kingfisher</a> library for the purpose of caching images in UICollectionView cells.</p>
  
  <p>I noticed that calling <a href="http://cocoadocs.org/docsets/Kingfisher/3.6.0/Extensions/ImageView.html#/s:vE10KingfisherCSo11UIImageView9kf_webURLGSqV10Foundation3URL_" rel="nofollow noreferrer"><code>kf_setImage</code></a> (assuming that the name of the cell called <code>listCell</code> and its ImageView called <code>imgMain</code>) as follows:</p>
  
  <pre><code>listCell.imgMain.kf.setImage(with: URL(string: "MY IMAGE URL"),
                               placeholder: UIImage(named: "PLACEHOLDER IMAGE"))
  </code></pre>
  
  <p>works fine, it does caches the image and display it when cell has been re-dequeued (when scrolling up and down, I can see the image directly without re-downloading it), <strong>but</strong> when I pull to refresh the collection view (recall the API with the same exact parameters, which means that it will return the same image urls) the images have been re-downloaded! I assume that the images already have been cached.</p>
  
  <p>To make it more clear, <a href="https://imgur.com/a/ikGXj" rel="nofollow noreferrer">this link</a> contains gif image that describes what am I facing. </p>
  
  <p>So, why the images get downloaded once again? is it the default behavior of the caching in Kingfisher? Is there any configuration that should edited to behave as I expect?</p>
  
  <p>I read the <a href="http://cocoadocs.org/docsets/Kingfisher/3.6.0/index.html" rel="nofollow noreferrer">library documentation</a>, but -unfortunately- I couldn't find and useful information related to what am I asking for.</p>