https://gerrit-review.googlesource.com/#/c/57231/ merged in a change to PatchSetCreatedEvent that adds a kind field and ChangeKind enum. This allows Gerrit to communicate the kind of change, and the listener to take certain actions based on this change kind.
Example if change kind is "NO_CODE_CHANGE" (i.e. just a commit message change) then the listener could decide not to trigger a build.
At this point, this is just a heads up, as this is in master, and not released but since it was "our" bug report that precipitated this change, we'd very much like to see this in Gerrit Trigger soon.