How does one change the identity of the HEAD (trunk) ?

[Julian Seward]

Greetings.

We have a project (valgrind) in which development proceeded
in the normal way on the trunk.  After a while we made a branch 
(VALGRIND_1_0_BRANCH) from which to do stable releases, and
that all works fine.

The plan was to continue development on the trunk (HEAD), as
you'd normally do.  Problem is, another branch (ERASER) appeared, 
and all interesting development happened there instead.

Now what we want to do is to throw away, in effect, the current HEAD
and turn the interesting ERASER branch into the HEAD.  

How can we do this?  

I already looked at 

   the cvs faq-o-matic, entry #36, 
   http://ccvs.cvshome.org/fom//cache/36.html
   which describes how to change the name of a branch,
   but my situation involves throwing away a branch and replacing
   it with a different one.

   I also looked at the section entitled
    "Some real-life problems (with solutions)"
   at http://cvsbook.red-bean.com/cvsbook.html
   and various other parts of this doc.  

>From neither of them was it possible to see how to do this,
nor whether it is even possible.

Can anyone offer guidance here?  We are prepared to mash around 
our repo contents by hand; whatever it takes.

Thanks,

J