how to `register' vc-hg-region-history in vc-region-history?

[Uwe Brauer]

Hi

I just tried out a new function
(right now I don't care much about keybinding and font locking

So the function 
(defun vc-hg-region-history (file buffer lfrom lto) 

Seems a natural generalization of vc-git-region-history  However I 
don't see how to tell vc-region-history to tell that the new 
function now exists. I tried to debug it


(defun vc-region-history (from to) 
   (vc-call region-history file buf lfrom lto) 

And there vc aborts for HG. What do I miss?

Uwe Brauer