revlog: add docket method to request new content files
If we want to write content into new files, we need to be able to ask for them.
Differential Revision: https://phab.mercurial-scm.org/D10867
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.