Previously, the `isCommitClosingPullRequest()` method (used in `ng-dev release` to detect whether a commit is closing a PR based on keywords found in the commit message) was only able to detect a subset of the keywords supported by GitHub. This is fine currently, because the merge script adds `PR Close #XYZ` when merging a PR, but it might break in the future. This commit makes the code more robust by ensuring the method can detect all keywords supported by GitHub for automatically closing a PR based on a commit message. Original discussion: https://github.com/angular/angular/pull/39135#discussion_r503440973 PR Close #39229