Re: commit dates, fundamentally those always change when rebasing because you're rewriting the commit object, but we don't touch the author date unless you explicitly reset it with metaedit
This is something you have to generally handle manually since absorb won't squash hunks with ambiguous targets, but I typically stack these branches and accept the dependency. I have had instances where this has backfired a little bit re: ordering but thankfully with JJ and the very patient little man in my computer named Codex it's easy to reorder them and end up with the same diff
Fwiw I generally solve this by using `jj commit` instead of `jj desc` unless I'm specifically targeting something that isn't my working copy. Technically it violates the "we want commands to be orthogonal" guideline we use to write Jujutsu (otherwise this would indeed be `jj desc; jj new`) but as a habit it's never let me down
Indeed, though I don't think it can create fixup commits if that's what you're looking for. However, it might work great for that if you pair it with jj-spr: https://github.com/LucioFranco/jj-spr
Megamerges are awesome, but what really makes them magical is when you start using `jj absorb`, which automatically splits and squashes your commit down to the nearest unambiguous commits and leaves anything that doesn't have an obvious place to live