title: Fish Shell: Conditional execution based on $status?
body: <p>In the fish shell the syntax for conditionals is hard to find. Does anyone have a link to an explanation of how to write an if, with ands and ors?</p>
  
  <p>In particular I would like to write</p>
  
  <pre><code>if not $status
    do a command
  end
  </code></pre>
  
  <p>To do a command when the previous command returned a non-success. How do I do that?</p>