GitHub has introduced a new feature called Stacked PRs, currently in private preview, to help developers manage large code changes more efficiently. According to theregister.com, the tool allows developers to split massive pull requests into smaller, more manageable chunks.
Under this new system, a pull request can be based on a previous pull request to form a continuous stack. Each individual PR in the stack can be reviewed and merged independently, provided that the preceding PRs in the stack are merged first. Users also have the option to merge the entire stack at once.
The primary goal of the feature is to encourage smaller, more discrete units of work. The outlet reported that the documentation emphasizes that each branch in a stack should represent a logical unit that can be reviewed on its own.
Traditionally, developers often wait until a feature is complete before submitting a PR, leading to massive, difficult-to-review code changes. This happens because developers frequently need to build new code on top of earlier changes that haven't been merged into the main branch yet.
A return to Phabricator workflows
While the feature is new to GitHub, the workflow is a revival of the 'stacked diffs' method used in older systems. The register notes that the concept was a core part of Phabricator, a toolset that included Differential, created by Facebook engineers Evan Priestley and Luke Shepard in 2007.
Priestley noted that the original motivation for building the tool was the time wasted waiting for code reviews. Although Phabricator ceased development in 2021, its influence remains. Jackson Gabbard, a former Facebook engineer, noted in an explainer that developers who used the Phabricator workflow often seek it out in their next roles.
GitHub is also introducing a new command-line interface (CLI) extension, `gh stack`, to simplify the process. While some developers on Hacker News suggested that Git's recent updates might make a specific CLI unnecessary, GitHub's Sameen Karim stated that the CLI is entirely optional and the feature can be used through the standard UI.
Karim also suggested that the feature is designed with the future of automation in mind. Speaking on LinkedIn, Karim noted that the main bottleneck in development is no longer writing code, but reviewing it. He added that the `gh stack` CLI is specifically designed to be used by AI agents.
