Readable tree diffing is a really interesting problem. When do you highlight lists? Do you highlight all the lists enclosing a modified subtree? What about comments?
I'm relatively happy with this case, but I think the outermost lists shouldn't be highlighted at all.
HN discussion of interesting technology demos for fifth graders:
https://news.ycombinator.com/item?id=20069714
One popular suggestion was browser tools, showing how web sites can be modified.
Another great idea is showing screenshots of bugs in realistic games and how they can go wrong.
I've been enjoying using Mercurial overall: I've found its abstractions pretty straightforward to learn, and it has all the staging, squashing features I like in git.
I do miss git's Committer vs Author though. Mercurial doesn't show who rebased your commit and modified it.
