What does it take to modernize an 8-year-old codebase? Stacks (on stacks). 🥞

GitHub's Copilot app case study shows how an AI coding task can grow without becoming one oversized change. After updating an old application's styling, the author found that replacing its aging react-bootstrap component library needed substantial additional work. They asked Copilot to put that replacement in a new session and a separate pull request built on the existing changes. The app carried the context forward and created the dependent work, according to the blog post.

A stack preserves that dependency: each pull request targets the preceding change's branch. The author could keep styling and library replacement as separate units to inspect and test, while the later work still used the earlier changes.