title: How to use the default value for an attribute set in nixos, and extend it
body: <p>The default value for <code>programs.zsh.shellAliases</code> is</p>
  
  <pre><code> { l = "ls -alh"; ll = "ls -l"; ls = "ls --color=tty"; }
  </code></pre>
  
  <p>which is nice.</p>
  
  <p>I want to extend the attribute set with</p>
  
  <pre><code>{ xclip = "xclip -selection clipboard"; paste = "xclip -out"; }
  </code></pre>
  
  <p>I know I can merge attribute sets with <code>//</code> and, because I know the default, I can just write down my desired attribute set explicitly.</p>
  
  <p>But is it possible to keep the default and extend it like this:</p>
  
  <pre><code> programs.zsh.shellAliases = [default] // { ... };
  </code></pre>
  
  <p>?</p>