title: What's the difference between 'pod spec lint' and 'pod lib lint'?
body: <p>Cocoapods provides two lint commands, <code>spec lint</code> and <code>lib lint</code>. What's the exact different between them, and in what scenario are they each used?</p>
  
  <p>I read the documentation (<a href="https://guides.cocoapods.org/terminal/commands.html#pod_spec_lint" rel="noreferrer">spec</a>, <a href="https://guides.cocoapods.org/terminal/commands.html#pod_lib_lint" rel="noreferrer">lib</a>), but I can not find the difference between them, and I do not understand why Cocoapods provides two command for the same thing.</p>