An outsider's perspective on Scion and Mononoke

Anthropic shared a blog post about their new centralized version control system, Scion. As someone who works on the Source Control team at Databricks, where a massive monorepo is being explored, I felt it would be helpful to share my thoughts on the matter. I encourage readers to first read Anthropic's post and Rain Paharia's follow-up, which discusses Scion's similarity to Mononoke.

Before diving into the details, it might be useful to know a bit about my background. I have not worked at Facebook but was greatly inspired by Durham Goode's talk, "Scaling Mercurial at Facebook" from Git Merge 2017. Goode, who was one of Facebook's most senior and longest-serving source control team members, delivered a talk that focused on both server-side and client-side improvements.

The talk highlighted several interesting aspects, such as solving push contention with server-side rebasing (pushrebase), employing scalable object storage for commits, and moving various source control queries to the server. On the client side, the presentation discussed smartlog and other CLI commands for easier history manipulation, which is preferable to rebasing in Git. However, beyond the technical aspects, what has consistently impressed me is the deep care for users that is evident in Goode's tone and words.

Goode's emphasis on user experience is a recurring theme that resonates throughout the talk. He described how hg smartlog provides users with a focused view of their branches and their relationship to the development trunk, making it intuitive for users to understand the concepts without needing to refer to a man page. Similarly, hg absorb automatically identifies the right commits in a stack to squash fixes into and rewrites history, making it easier for users to work with stacked changes.

These examples demonstrate the type of user-friendly interface that we aspire to build for our users at Databricks. We aim to create intuitive and accessible tools that enable both novice and power users to navigate and manage their codebase with confidence. This philosophy mirrors Goode's vision and is something I believe is crucial for the user experience in version control systems.