As part of the 22FEB2016 update the support for site specific url shares is now available.
It has always been possible to have the same url on many documents i.e. /app - but when rendering a website it would always find the first document in the space associated with the site.
Now during rendering it checks to see if there is a document linked to the site that has the matching share URL and shows it - if not, it falls back to the existing mechanism of space level match.
This is particularly handy in url based app production - so you can now have a "lab" version of the page and also one that is in production.
will now render differently, but the controllers that are linked to the "app" context can be the same and transported without change between "lab" and "prod".