subrepo: remove superfluous newline from subrepo prompt

ui: show prompt choice if input is not a tty but is forced to be interactive The tests often set ui.interactive to control normally interactive prompts from stdin. That gave an output where it was non-obvious what prompts got which which response, and the output lacked the newline users would see after input. Instead, if the input not is a tty, write the selection and a newline.

merge with stable

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.