Previously, we relied only on the regex to match a review request ID in the

commit message. Now, we use the regex to try to find a matching review request

ID in the commit message, and if no match is found, we then use the commit ID

to try to find a matching review request.

I pushed different commits to a GitHub repository with the post-receive webhook

enabled (and saw the expected behaviour):

- Commit that did not match the regex but matched a review request's commit ID

- Commit that did not match the regex and did not match a review request's

  commit ID

- Commit that matched the regex