[swisspol]

GitUp uses libgit2 under the hood. GitUpKit is an Obj-C wrapper I wrote at the time to make it much easier to use.

Unlimited undo / redo is achieved by taking a snapshot of the entire repo before and after any operation (e.g. checking out the repo or creating a branch etc...). The inspiration I had at the time was that is it is trivially cheap to take such snapshots: essentially all you need is a list of all the refs.

Then when you need to undo, you have 3 things: 1 - current state of all the refs in the repo 2 - state of all the refs from the before snapshot 3 - state of all the refs from the after snapshot Compute the delta between 3 -> 2 and apply on top of 1.

The same technique allows to do the Time Machine feature.