post/changed is called for both X->SUCCESS, or SUCCESS->X.
X being typically failure or unstable.

As a user, I would like to have a very straightforward way to express that I'm only interested in the X->SUCCESS direction, because actually the SUCCESS->X is already covered by post/unstable or post/failure blocks.

My use case is the following: I want to send an email for failures, unstable, and back to success. For the reason explained above, I don't want to send a notification when the status changes from success to something else, because then I would send two notifications instead for one actual event. And it would lower the signal/noise ratio.
I think it could be fullfilled like:

post {
    // we could also add previousState below, btw. But in that case it would 
    // force me to express all the possible previous statuses, which I don't 
    // care about here
    changed(newState: SUCCESS) {
        mail to: NOTIFICATION_TARGET, subject: "BACK TO SUCCESS! YAY!: .......
    }
    failure {
        mail to: NOTIFICATION_TARGET, subject: "FAILURE: .......
    }
    // ...
}

Thanks!