Comment 5 for bug 202420

Launchpad can always guess, but it can never know for sure.

Here's one way to guess. We can check to see if any of the revisions that are in feature-x-refactor but not in trunk are parents of revisions in feature-x-itself. (The clunkiness of that sentence is some measure of the clunkiness of the guesswork.) The problem with this way of guessing is that sometimes multiple branches will fit the bill.