changectx: use unfiltered changelog to walk ancestors in annotate
Since we are only walking ancestors, it is safe to use an unfiltered repository.
(Because if the original rev is not filtered, none of its ancestors will be).
Differential Revision: https://phab.mercurial-scm.org/D7501
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.