> I think "documentation sources" is a bit vague.
I don’t know.  I probably wrote it under the assumption that the audience of this doc was developers, who already know that programmers don’t write HTML manually but generate it, and just need to know where to find the sources.  To a C programmer wanting to fix a bug, we just say “the sources for X are in Include and Modules”, and it’s enough.

Thinking about it, the assumption is probably bad.  Sometimes we have to explain to new contributors where to find a Python module in the repo and how to write a test, so it would probably be better to explain more.  Here’s my draft, feel free to improve my patch with it (there may be duplication) and commit the result when you two are in agreement while I’ll be offline.

  The documentation in HTML, PDF or epub format is generated from text files
  written using the :ref:`reStructuredText format <markup> and contained in
  the :ref:`CPython Mercurial repository <setup>`.