new docs are not converted to html

[Ian Clatworthy]

Alexander Belchenko wrote:
> There is 2 new txt files in directory doc\en\user-reference\
> index.txt
> hooks.txt
> 
> They both are not converted to html during `make docs`.

Looking at your patch to fix this, I think that hooks.txt should be an
online topic - part of bzrlib/help_topics.py - instead of a separate
file. It will then automatically become part of the generated User
Reference. As well as enhancing the online help, this approach removes
the extra level of index that has been introduced (vs 0.90).

If everyone is good with that, I'll update HACKING to be more explicit
about our documentation rules.

Further comments in the patch email.

Ian C.