Sphinx's latex builder doesn't like our cross-references to .html files, leading to tons of warnings like this:
writing... /Users/user/hacking/bazaar/bzr/doc/en/user-guide/introducing_bazaar.txt:: WARNING: unusable reference target found: ../mini-tutorial/index.html
/Users/user/hacking/bazaar/bzr/doc/en/user-guide/introducing_bazaar.txt:: WARNING: unusable reference target found: ../quick-reference/index.html
/Users/user/hacking/bazaar/bzr/doc/en/user-guide/introducing_bazaar.txt:: WARNING: unusable reference target found: ../user-reference/index.html
/Users/user/hacking/bazaar/bzr/doc/en/user-guide/core_concepts.txt:: WARNING: unusable reference target found: specifying_revisions.html
/Users/user/hacking/bazaar/bzr/doc/en/user-guide/core_concepts.txt:: WARNING: unusable reference target found: zen.html#understanding-revision-numbers
Docutils doesn't seem to have any facilities that would be of any real use here. Sphinx does (see <http://sphinx.pocoo.org/markup/inline.html#cross-referencing-syntax>), but of course docutils won't grok that on its own, and it seems that we still support using plain docutils for html conversion, so I'm not sure how to solve this. (A sphinx extension to automatically rewrite these references, maybe?)
