Ask HN: Who uses custom versions of common tools in their build pipeline?

I&#x27;m going to participate in a debate on monolithic vs many smaller repositories.<p>One of my points is that many companies does not have a scale where investing heavily in custom tooling has a feasible ROI.<p>I know that Facebook builds and ships the very newest Mercurial with extensions. https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=gOVD-DrUpwQ&amp;t=169s<p>Uber uses ( or has used ) a custom build of Docker to do some scrubbing of build-time secrets.<p>What other companies do you know of that uses custom built versions of common tools like Git? And for what purpose?<p>I look forward to seeing some cool examples of custom tooling.