Documentation sidebar changes from page to page
The documentation at https://buildstream.gitlab.io/buildstream/ has a table-of-contents sidebar which Sphinx autogenerates.
Currently the sidebar only shows topics from the current page. It should instead show the table of contents of the entire manual on every page, which would make it easier to navigate between pages.
This looks quite difficult to achieve, nobody has yet figured out how to get Sphinx to do what we want.