This folder includes a hidden directory .hg used by Mercurial, a source code management system that is really simple to use. (Google for Mercurial: The Definitive Guide for a nice book that gets you started fast.)

I'm a Mercurial newbie. As of now, Halls of Mist doesn't yet have a public Mercurial repository. It will probably have one soon.

If you want to share your new features or bugfixes with me before that, you may for example "hg commit" your changes and then send the archived folder to miihkali.lehtinen@gmail.com. (Gmail blocks attachments named *.zip, rename it to .zippo or something.)