The commit activity in the PR activity feed doesn't align with the commits list on the PR

Issue Summary

The commit activity in the PR activity feed doesn't align with the commits list on the PR.

This is reproducible on Data Center: (yes) / (no) no

Steps to Reproduce

1. Create a pull request
2. While the pull request is open, clone the PR source branch repository
3. add local commits (for example in the order of x, y, z commits. z being the latest)
4. push the changes to the remote repository. x, y, z commits will be pushed to the remote repository in a batch and will be shown on the commits page and in the PR commits list.

Expected Results

The PR activity feed should show UPDATED: the pull request with 3 commits: x, y, z

Actual Results

The PR activity feed showing UPDATED: the pull request with 1 commit: z

Workaround

We need to refer to the commits list in the PR instead of the PR activity feed, to view the local commits pushed to the remote in a batch.