Change close after merge to close before merge for Mercurial

When using the close after merge option for pull requests in hg you first do the merge and close the branch after that. This leaves the closing changeset as an unmerged head.
This not only looks messy but also leads to a "creates new remote head" problem if you later create a branch with the same name. You then have to merge the closing changeset or force push the other head.
If you would change to first closing the branch and then merging the closing changeset this problem would go away and the tree would also look much better.