[Wilfred]

I've looked at several tree diffing papers, including Chawathe et al, but it's not always easy to assess whether their approach would suit difftastic.

I know that sdiff by Arun Isaac is based on applying that paper to Scheme: https://archive.fosdem.org/2021/schedule/event/sexpressiondi... , although he also reports performance challenges.

Most tree diffing papers that I've seen focus on either (1) providing a minimal diff and accepting the performance cost or (2) providing a relatively minimal diff and focusing on the performance.

I've generally found that you need a minimal diff to get a good result, so papers in (2) are less applicable. I've also found several cases where there are several possible minimal diffs, but there's a clear 'correct' answer from the user's perspective.

Difftastic doesn't handle moves: the edit set is add, remove, or replace similar comment. If you reorder functions, it will take the largest unchanged subset. Moves are hard to model in a diffing algorithm, but they're also very hard to display coherently in the UI.

I know a few code forge websites (e.g. Phabricator) show moves in a fairly comprehensible way, although they're all based on line-based diffs.