Add Changesets functionality to Merge Requests
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Context
A key challenge that a lot of contributors and maintainers experience with Merge Requests and similar functionality provided by Git-based software development platforms is around the back-and-forth comments while changes are being merged, which essentially makes the MR experience effectively one giant mutable changeset.
This concern was also highlighted by Mitchell Hashimoto in his blog post dated September 30, 2023, where he captured the challenges and also provided recommendations based on approaches taken by other platforms.
Problem to solve
Feedback and the state of the MR aren’t tied together. In particular, the state of the MR can get out of sync with feedback/comments, which can make it difficult to review. Some challenges as highlighted in the blog:
- A review can become partially outdated and feedback may not make sense in the context of the changes a contributor pushed.
- Work-in-progress commits towards addressing review feedback become visible when the branch is pushed. This forces contributors to address all feedback in a single commit, or for reviewers to deal with partially-addressed feedback.
- You can't easily scrub to prior states of the MR. If you want to review a set of earlier commits while ignoring later commits, you only get the code changes, and you don't also get the point-in-time reviewer feedback.
Proposal
The proposed solution to this experience is using Changesets.
Aside from addressing the challenges outlined above, one major advantage of this approach lies in the fact that the contributor can post multiple changesets with differing approaches to a problem in a single MR and the maintainer can potentially choose the non-latest changeset as the set of changes they want to see merged.
Additional Details
The changesets approach is also employed by other Git based tools such as Gerrit, where each "Change Set" encapsulates a single coherent change to the codebase that is proposed by a contributor. Change Sets in Gerrit offer several benefits that enhance the code review process:
- Focused Reviews: By encapsulating a specific change, reviewers can concentrate on understanding and evaluating just that change, rather than an entire branch of work.
- Clear History: Each Change Set represents a logical unit of work, which leads to a cleaner, more understandable commit history.
- Continuous Integration: The iterative nature of Change Sets aligns well with continuous integration practices, allowing for regular testing and review of small changes.
Phabricator, a pre-commit code review workflows service, also provides a similar experience.