[Zope-CMF] workflow transition url

[Mark Gibson]

In the portal_workflow transition properties tab, there is a field 
titled URL (formatted).   I've seen it used like this:

%(content_url)s/content_revise_form

So, I can use content_url to get the url of the content.  I can also 
use 'content' to get the object.  How would I access the id of the 
content in this field?  %(content/id) doesn't work.  Is there a list 
anywhere of the available variables ( like content_url )?

Thanks,
Mark