Hunting the Shmoo

You felt it. The shift. That your role has fundamentally changed thanks to LLMs. It first entered your subconscious when you realized how easily you can now crank out PRs. You felt it more concretely (and less enthusiastically), as a reviewer when you opened your laptop one morning and noticed your review queue was double what it normally is thanks to everyone else cranking out PRs. And you feel this pervasive, general sense of friction.

It’s difficult to pinpoint exactly where this friction is coming from. Depending on the repository size and CI setup, it will be slightly different for everyone. It might involve longer review times or slipping review standards. You might be noticing more merge conflicts and merge related CI failures. Perhaps there are more failures sneaking through to main or CI is taking longer to give you results. You almost certainly feel the grind. People are on edge, tired; developers are pulling in opposite directions.

Here’s what LLMs shifted. The bottleneck is no longer producing code. The bottleneck is integrating it. The friction we’re feeling is a result of more PRs, more ideas, more reviews, more disagreements all made possible thanks to LLMs. In short, the problem can best be summarized by Figure 1:

But we’re living in a moment where many folks haven’t realized this yet, and are still under the impression that their job is to produce code.

It’s not. Your new job is to integrate it.

One of the pleasures of working at Mozilla, has been learning and using the Mercurial version control system. Over the past decade, I’ve spent countless hours tinkering my worfklow to be just so. Reading docs and articles, meticulously tweaking settings and even writing an extension.

I used to be very passionate about Mercurial. But as time went on, the culture at Mozilla started changing. More and more repos were created in Github, and more and more developers started using git-cinnabar to work on mozilla-central. Then my role changed and I found that 90% of my work was happening outside of mozilla-central and the Mercurial garden I had created for myself.

So it was with a sense of resigned inevitability that I took the news that Mozilla would be migrating mozilla-central to Git. The fire in me was all but extinguished, I was resigned to my fate. And what’s more, I had to agree. The time had come for Mozilla to officially make the switch.

Glandium wrote an excellent post outlining some of the history of the decisions made around version control, putting them into the context of the time. In that post, he offers some compelling wisdom to Mercurial holdouts like myself:

I’ll swim against the current here, and say this: the earlier you can switch to git, the earlier you’ll find out what works and what doesn’t work for you, whether you already know Git or not.

When I read that, I had to agree. But, I just couldn’t bring myself to do it. No, if I was going to have to give up my revsets and changeset obsolesence and my carefully curated workflows, then so be it. But damnit! I was going to continue using them for as long as possible.

And I’m glad I didn’t switch because then I stumbled upon Jujutsu.

Have you ever submitted a patch to Phabricator only to have reviewbot reveal dozens of lint errors all over? Or worse yet, have you landed before reviewbot had a chance to analyze your patch and been backed out over lint failures? If so fear not, we’ve all been there. Still, it’s hard not to feel a little embarrassed when it happens. Luckily for you, it’s pretty easy to eliminate the possibility of it ever happening again!

If you’re working with mozilla-central on Windows and followed the official documentation, there’s a good chance the MozillaBuild shell is running in the default cmd.exe console. If you’ve spent any amount of time in this console you’ve also likely noticed it leaves a bit to be desired. Standard terminal features such as tabs, splits and themes are missing. More importantly, it doesn’t render unicode characters (at least out of the box).

Luckily Microsoft has developed a modern terminal that can replace cmd.exe, and getting it set up with MozillaBuild shell is simple.