Not only fossil+venti, the old standalone cached-worm file server, and its user-space port cwfs were also built around versioning.
By default, the cached-worm systems are dumped at 5am every day in the morning, meaning you can access your files as they were at 5am every day. You can manually dump them whenever you please, of course. These dumps are cheap, but not as cheap as fossil or ZFS (or git) snapshots. Unlike ZFS (not sure about git), these dumps are immutable, you can't delete them.
With fossil+venti, you still get daily dumps, but you also get finer grained ephemeral snapshots. By default at 15 minute intervals, I used to set them at 5 minutes. You can control how long you want to keep these in fossil, I kept mine for 3 months. The dumps are venti are immutable. These are very very cheap, and these systems also do deduplication, by default.
I don't run fossil anymore, I like the features, but reliability was less than stellar for some people, and the performance is much lower than cwfs, which is what I use now. Cwfs is very fast, rock solid, and very easy to recover in case of a catastrophe. I miss ephemeral snapshots, but cwfs dumps are cheap enough I can run them for what in a normal system you'd do "commits" for.
I miss all these features when I am forced to use Unix. Git does two things, history preservation and patch management. For history preservation, nothing beats the Plan 9 system. What git does better is patch management. I think it's valuable not to conflate these two concepts and create tools that can solve each one well, and work well together.
By default, the cached-worm systems are dumped at 5am every day in the morning, meaning you can access your files as they were at 5am every day. You can manually dump them whenever you please, of course. These dumps are cheap, but not as cheap as fossil or ZFS (or git) snapshots. Unlike ZFS (not sure about git), these dumps are immutable, you can't delete them.
With fossil+venti, you still get daily dumps, but you also get finer grained ephemeral snapshots. By default at 15 minute intervals, I used to set them at 5 minutes. You can control how long you want to keep these in fossil, I kept mine for 3 months. The dumps are venti are immutable. These are very very cheap, and these systems also do deduplication, by default.
I don't run fossil anymore, I like the features, but reliability was less than stellar for some people, and the performance is much lower than cwfs, which is what I use now. Cwfs is very fast, rock solid, and very easy to recover in case of a catastrophe. I miss ephemeral snapshots, but cwfs dumps are cheap enough I can run them for what in a normal system you'd do "commits" for.
I miss all these features when I am forced to use Unix. Git does two things, history preservation and patch management. For history preservation, nothing beats the Plan 9 system. What git does better is patch management. I think it's valuable not to conflate these two concepts and create tools that can solve each one well, and work well together.