Disable backing out merges?

[Dominik Psenner]

>As far a I can tell closing a branch doesn't do much... Closed
>branches still count in the head count, which is quite counter
>intuitive to me...
>
>If all heads of a given branch are closed then the corresponding
>branch is hidden when calling hg branch, right? Is that the whole
>point of closing a branch?

It doesn't show up in "hg heads", either.