Upgrading from using only the 'gerrit-trigger-plugin' I lose the ability to determine which gerrit event triggered the job.

I need this information to decide which type of pipeline to run (build packages when changes are opened, promote packages when they successfully pass the verification and review stage):

if (env.GERRIT_EVENT_TYPE == "patchset-created") {
    runBuild()
}
else if (env.GERRIT_EVENT_TYPE == "change-merged"){
    runPromote()
}

At least this environmental variable is not in the list of supported env vars... If there is any other way to get this information that I might have missed then please let me know! 

[update: maybe the 'change-merged' event won't work for my use case since the job is automatically closed when the change is closed.  Instead I think JENKINS-60365 might better suit my needs]