> What is missing, from the users point of view, when they model commits as diffs+parents vs as snapshots? With the wrong mental model it's harder to predict w

> What is missing, from the users point of view, when they model commits as diffs+parents vs as snapshots? With the wrong mental model it's harder to predict what operations are expensive. If "git checkout <SHA>" truly did have to replay all diffs from the beginning of time, it would be a very expensive operation that is best avoided unless you absolutely need it. But in practice it is a very fast operation (one of the fastest) that there is no need to shy away from.