Fossil is a source-code management system. It was originally built to manage SQLite in a similar way that git was built to manage the Linux kernel.
In addition to managing source code, Fossil features an integrated bug-tracking system, wiki, and web-based UI.
A Fossil repo is stored as a single SQLite archive which is extracted into an active workspace.
Some curated links
fossil vs. git, a useful primer for understanding fossil from a git perspecitve. Brings up the classic "Cathedral vs Bazaar" metaphor in a way I never thought about before.