cmdutil: changeset_printer: use methods of filectx/changectx. This allows extensions that modify changeset metadata (e.g. description) by overriding methods of changectx to get consistent behavior from all log-like commands, regardless of whether templates or styles are used. Without this, overriding changectx methods works if you use styles or templates, but not with default log format. This meant adding filectx.extra() for consistency with changectx.

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.