Visible on D18123 on this install.
Oh, this is actually the Mercurial flavor of this action. We have this one in the Git flavor, which is why I was surprised:
// TODO: This temporarily disables this action, because it doesn't work // and is confusing to users. If you want to use it, comment out this line // for now and we'll provide real support eventually. return;
I'm probably just going to remove these wholesale, the upstream version doesn't precisely replace them but has proven stable, at least.