Fossil tracks issues (tickets), documentation, and wiki pages at the same level as it tracks code, so when you clone a Fossil repo, everything gets downloaded to your local computer. You can then respond to tickets and perform repo maintenance offline, syncing everything to the server when you're back up.
Edit: A few weeks ago I got a job a one-hour train ride away. I can commit, close tickets, and write docs on my way in, sync everything to the internet when I get to work, then do the same on my way back - even though I don't have a net connection during my commute. It works great. (Ok, not as good as not having to travel at all, but great nonetheless!)