title: Emacs using path relative to init.el file
body: <p>I am storing my Emacs <code>init.el</code> file in Dropbox, along with dependent files like color themes.  Say I have a directory <code>~/Dropbox/emacs</code> whose content is something like:</p>
  
  <pre><code>.
  ├── init.el
  └── themes
      └── zenburn-theme.el
  </code></pre>
  
  <p>Then on my Linux machine I simply have a symlink from <code>~/emacs.d/init.el</code> to <code>~/Dropbox/emacs/init.el</code>, which works just fine.  In my <code>init.el</code> though, I'd like to be able to load the theme using a path relative to the <code>init.el</code> file itself.  i.e. I'd like to do something like:</p>
  
  <pre><code>(add-to-list 'custom-theme-load-path "./themes/")
  (load-theme 'zenburn t)
  </code></pre>
  
  <p>My use of <code>"./themes/"</code> as a path relative to <code>init.el</code> seems to not work as anticipated though.  I can change this to:</p>
  
  <pre><code>(add-to-list 'custom-theme-load-path "~/Dropbox/emacs/themes/")
  (load-theme 'zenburn t)
  </code></pre>
  
  <p>and it will work.  However, I'd prefer a notation that is relative to the <code>init.el</code> file.  This way, if I for example decide at a later date to have all my <code>init.el</code> file and other related files somewhere other than Dropbox, I can simply copy the entire directory and rewire the single init.el symlink without having to change all the references to <code>~/Dropbox</code>.</p>
  
  <p>So,</p>
  
  <ol>
  <li>Is there a way to reference directories relative to the <code>init.el</code> file?</li>
  <li>As someone who is not particularly well versed in Lisp syntax, what would this look like in the specific example above (adding a custom theme path)?</li>
  </ol>