Mercurial: Set Bookmarks to follow the tip of a branch of a repository

In relation to the open enhancement request #6705, a customer is asking if there could be a way to set bookmarks to follow the tip of a branch of a repository.

Note from the customer

Note that when there is only one head in the branch of the main repository, it is worse because we don't see the bookmarks at all in the "create a pull request page". For example, if there is a bookmark master, we can not create a pull request from this bookmark (which is what we want) so we cannot see the message There are no changes to be pulled. The problem is then that the bookmark master is not updated and doesn't follow the tip of the default branch of the main repository.

We would really need such master (or @) bookmark following the tip of the default branch of the main repository to easily update the cloned repositories to this point to start a new work.