I would like to convert my Subversion repository to Mercurial. I have a pretty big web project divided into many different folders. In Subversion I was able to set per directory permissions for a repository. For example, I could say that a new developer could only read and write a subset of all the project's directories, using Subversion's path-based authorization. I could "hide" certain directories containing sensitive parts of the code from the developer, so that he wouldn't be able to see their contents, nor commit any changes to them.
Is it possible to have a similar setup in a single Mercurial repository?