rebase: use obsolete.isenabled() to check for experimental.allowdivergence
Now that obsolete.isenabled() can also check if divergence is allowed, let's
use it for consistency. Other experimental.evolution options are already
checked via this function.
Differential Revision: https://phab.mercurial-scm.org/D11221
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.