help: basic support for showing only specified topic sections For instance, 'hg help config.files' will show only the Files section.

help: use OS containers for config file lists

help: support OS-specific help sections Containers of the form: .. container:: verbose.<os> are shown by default on the given OS (or with -v).

minirst: allow multiple container types for prune If we have a container of type x.y, then we can preserve it by keeping x or y.