Even if you're working on one single thread of development, jj is easier and more flexible than git though. That it works better for super complicated workflows is just a bonus.

jj reduces mental overhead by mapping far more cleanly and intuitively to the way people tend to work.

This is a little weird at first when you’ve been used to a decade and a half of contorting your mental model to fit git. But it genuinely is one of those tools that’s both easier and more powerful. The entire reason people are looking at these new workflows is because jj makes things so much easier and more straightforward that we can explore new workflows that remove or reduce the complexity of things that just weren’t even remotely plausible in git.

A huge one for me: successive PRs that roll out some thing to dev/staging/prod. You can do the work all at once, split it into three commits that progressively roll out, and make a PR for each. This doesn’t sound impressive until you have to fix something in the dev PR. In git, this would be a massive pain in the ass. In jj, it’s basically a no-op. You fix dev, and everything downstream is updated to include the fix automatically. It’s nearly zero effort.

Another is when you are working on a feature and in doing so need to add a capability to somewhere else and fix two bugs in other places. You could just do all of this in one PR, but now the whole thing has to b reviewed as a larger package. With jj, it’s trivial to pull out the three separate changes into three branches, continue your work on a merge of those three branches, and open PRs for each separate change. When two of them merge cleanly and another needs further changes, you just do it and there’s zero friction from the tool. Meanwhile just the thought of this in git gives me anxiety. It reduces my mental overhead, my effort, and gives overburdened coworkers bite-sized PRs that can be reviewed in seconds instead of a bigger one that needs time set aside. And I don’t ever end up in a situation where I need to stop working on the thing I am trying to do because my team hasn’t had the bandwidth to review and merge my PRs. I’ve been dozens of commits and several stacked branches ahead of what’s been merged and it doesn’t even slightly matter.

"Merge 2 branches" is already far from being a primitive. A git repository is just a graph of snapshots of some files and directories that can be manipulated in various ways, and git itself is a bunch of tools to manipulate that graph, sometimes directly (plumbing) and sometimes in an opinionated way (porcelain). Merging is nothing but creating a node (commit) that has more than one parent (not necessarily two) combined with a pluggable tool that helps you reconcile the contents of these parents (which does not actually have to be used at all as the result does not have to be related to any of the parents).

(you may know that already, but maybe someone who reads this will find this helpful for forming a good mental model, as so many people lack one despite of working with git daily)