How to Resume Review Process After Updating a Pull Request at GitHub

Collaborative software development often involves code reviews to ensure code quality and maintainability. GitHub facilitates this process excellently with its Pull Request (PR) review system. However, a common question arises: What happens after a pull request is updated? How can you resume or continue the review process seamlessly? This article unpacks that scenario with a focus on best practices and techniques suited for both contributors and reviewers.

Understanding GitHub Pull Requests

Before diving into the review process, let's understand what a Pull Request is. In the Git model, developers usually work on branches. After finishing a feature or a fix, these changes need integration into the main codebase. A Pull Request is a proposal to merge changes from one branch to another, usually from a feature branch to a main branch.

1. Creating a Pull Request:
   A developer first commits changes to a feature branch and then opens a Pull Request against the main branch.
2. Review Process:
   Other developers or maintainers review the changes, providing feedback or directly suggesting changes.
3. Updating the Pull Request:
   The PR author can update the pull request by pushing additional commits to the source branch.

What Happens When a Pull Request is Updated?

When a PR is updated with new commits, GitHub reflects these changes directly in the existing Pull Request. This may require the review process to be revisited. Here’s how you can efficiently manage this:

1. Automatic Dismissal of Previously Approved Reviews:
   If a pull request that had been previously approved is updated with new commits, its status will change from `Approved` to `Changes Requested` or remain `Pending Review`, depending on your repository settings. This is to ensure that the new changes are also reviewed adequately.
2. Notifications:
   GitHub will notify all reviewers of the new changes so they can revisit the PR and ensure everything is still in good standing with the project's guidelines.

Resuming the Review Process

1. Re-opening the Pull Request URL:
   You can continue your review from the exact point where you left using the URL of the pull request, which remains constant.
2. Viewing Commit Differences:
   GitHub offers options to view changes since your last review. You can look at all changes or just the incremental changes. To see incremental differences, navigate to the 'Files Changed' tab, and choose the `Changes from all commits since you last viewed` option.
3. Reconfirming Feedback:
   With updates to a PR, old comments may become outdated. You can mark conversations as resolved or reopen them for further discussion as necessary.
4. Re-approving the Pull Request:
   With any new changes, reviewers must again approve the pull request or request further changes before it can be merged.

Example: Updating a Pull Request

Suppose you have a feature branch `feature-123`:

1. You pushed initial changes to the branch and opened a pull request.
2. After a review, you make additional changes in response to the feedback:

• Contributors should make a habit of pushing focused, clear commits. It is helpful for reviewers if each commit has a specific purpose.
• Reviewers should re-examine updated portions and validate that newly added changes align with project goals and do not introduce other issues.