I'm trying to set up Apache to use the VirtualDocumentRoot directive but my sites aren't all exactly the same. Most of the sites have a drupal folder which should be the root but there are a few really old drupal sites, a few rails sites, some django sites, etc. that want the Document root to be / or some other folder.

Is there a way to set up VirtualDocumentRoot based on a conditional or is there a way to use RewriteRule/Cond to detect that / is the incorrect folder if there is a drupal folder or a public folder?

Here's what I have so far:

<VirtualHost *:80>
  # Wildcard ServerAlias, this is the default vhost if no specific vhost matches first.
  ServerAlias *.unicorn.devserver.com

  # Automatic ServerName, based on the HTTP_HOST header.
  UseCanonicalName Off

  # Automatic DocumentRoot.  This uses the 4th level domain name as the document root,
  # for example http://bar.foo.baz.com/ would respond with /Users/vosechu/Sites/bar/drupal.
  VirtualDocumentRoot /Users/vosechu/Sites/%-4/drupal
</VirtualHost>

Thanks in advance!

-Chuck