OwlBot: PR title should contain highest level of conventional commit detected

[bshaffer]

The Problem

When an OwlBot PR contains multiple commits, the PR title (and therefore the conventional commit type) is simply the first CL in the list. For example, in this Compute PR, you'll see the PR title uses fix:, even though further down the commit list, there are several feat: CLs merged:

TITLE: fix(compute): revert proto3...
DESCRIPTION:
fix(compute): replace missing REQUIRED for parent_id 
...
feat: update compute API to revision 20220322 
...

As a result, the next version of our google/cloud-compute library which got released was only incremented a patch release (1.0.2) instead of a feature release (1.1.0) like we want and expect.

The Solution

Change the PR title to properly represent the highest level of conventional commit detected. In this case, it would be a feat instead of a fix. This would ensure that when the PRs are merged, a proper version is tagged with the next release.

[chingor13]

If the PR body had been used as the commit message, then every one of the fix/feat messages would have made it to the release notes (which is likely what you want). See https://github.com/googleapis/release-please#what-if-my-pr-contains-multiple-fixes-or-features. An easy way to do this is to use the merge-on-green bot (adding the automerge label).

As it happened, the default squash/merge button was used in the UI. It's possible to fix this after the fact, by updating the PR body. See https://github.com/googleapis/release-please#how-can-i-fix-release-notes.