In git you can use merge commits as your "summary" and `--first-parent` or other DAG depth flags to `git log` (et al) to see only summaries first. From the command line you can easily add that to key aliases and not worry about. I think that if GitHub had a better way to surface that in their UI (ie, default to `--first-parent` and have accordions or something to dive deeper), there would be a lot less squashing in git life. (Certainly, I don't believe in branch squashing.)

The DAG is already powerful enough to handle both the complicated details and the top-level summaries, it's just dumb that the UIs don't default to smarter displays.

(I find git stash essential given that `git add --interactive` is a painful UX compared to darcs and git doesn't have anything near darcs' smarts for merges when pulling/merging branches. Obviously, your mileage will vary.)