Unable to a new branch with VC commit

[Tero Mononen]

Dear Emacs people,

Most likely I'm doing something wrong but I don't know what.

I haven't managed to create a new Mercurial branch in Emacs. According 
to manual [1] it should happen with C-u C-x v v. It does request "New 
revision or backend". I give name of the new branch, and then commit 
changes. Surprisingly, commit ends up to the active branch instead of 
the new one. I.e., it completely ignores my input.

I tested the same procedure also with Git and the result was also the same.

My workaround is to change branch manually with "hg branch" command and 
then use VC in emacs. But, I'm wondering how to do the whole process 
with VC.

[1] 
https://www.gnu.org/software/emacs/manual/html_node/emacs/Creating-Branches.html#Creating-Branches