fossil大概是自带bug tracking, wiki, forum, email alerts, chat, and technotes的git, 只有一个可执行文件，有内置的http服务器，把.fossil文件clone下来就能备份整个论坛;fossil 把repo（包括论坛）存储在一个sqlite文件里，用fossil open可以解包，因此非常适合自托管
在 https://chiselapp.com/ 可以host fossil
What Is Fossil?
Fossil is a simple, high-reliability, distributed software configuration management system with these advanced features:
Project Management - In addition to doing distributed version control like Git and Mercurial, Fossil also supports bug tracking, wiki, forum, email alerts, chat, and technotes. Built-in Web Interface - Fossil has a built-in, themeable, extensible, and intuitive web interface with a rich variety of information pages (examples) promoting situational awareness. This entire website is just a running instance of Fossil. The pages you see here are all wiki or embedded documentation or (in the case of the download page) unversioned files. When you clone Fossil from one of its self-hosting repositories, you get more than just source code - you get this entire website. All-in-one - Fossil is a single self-contained, stand-alone executable. To install, simply download a precompiled binary for Linux, Mac, or Windows and put it on your $PATH. Easy-to-compile source code is also available. Self-host Friendly - Stand up a project website in minutes using a variety of techniques. Fossil is CPU and memory efficient. Most projects can be hosted comfortably on a $5/month VPS or a Raspberry Pi. You can also set up an automatic GitHub mirror. Simple Networking - Fossil uses ordinary HTTPS (or SSH if you prefer) for network communications, so it works fine from behind firewalls and proxies. The protocol is bandwidth efficient to the point that Fossil can be used comfortably over dial-up, weak 3G, or airliner Wifi. Autosync - Fossil supports "autosync" mode which helps to keep projects moving forward by reducing the amount of needless forking and merging often associated with distributed projects. Robust & Reliable - Fossil stores content using an enduring file format in an SQLite database so that transactions are atomic even if interrupted by a power loss or system crash. Automatic self-checks verify that all aspects of the repository are consistent prior to each commit. Free and Open-Source - 2-clause BSD license.
as for demo, https://fossil-scm.org/ itself is setup by fossil
you can check the forum in https://fossil-scm.org/forum/forum
you can use 'fossil clone https://fossil-scm.org yourproject.fossil' to get a local copy of the repo(site)
typing 'fossil ui yourproject.fossil' and you can visit your forum on localhost:8080
in an empty directory, type 'fossil open path-to-yourproject.fossil' to 'extract' it here.