hgweb: support multi-level repository indexes by enabling descend and collapse The descend option in hgweb can be used to display all reachable repositories within a directory hierarchy if set to True. However, all reachable repositories, regardless of their depth below the root of the hierarchy, are then listed at the same level - expanded - in the hgweb interface. This patch adds support for showing only each level of a directory hierarchy, with subrepositories being shown alongside their parent repositories only at the appropriate level (because there is no way to navigate to subrepositories from within repositories), and the contents of directories hidden - collapsed - behind a link for each directory. To enable this multi-level navigation, a new option called collapse must be set to True when the descend option is set to True.