One thing I've wanted is the ability to group commits into a mega commit. So the history of little changes remains, but as you are scrolling you don't see all of them.
This is an interesting idea... jj has a templating language, but it's not stateful, so you couldn't like, hide some commits based on other commits, for example. But I'll file this away...
That's called a merge commit. You can even group them further by creating merges of merge commit. It requires you to merge in the right direction though.
--first-parent? --simplify-by-decoration? It doesn't hide them by default yes. It does have several paragraphs with all the ways how to simplify the history.
