stream-clone: directly use `_entries_walk` to generate stream-v2
This does not requires that much changes and will give us much more
flexibility, like improving revlog handling to gracefully handle race
situation.
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.