ancestor path / revision

When doing a checkout/update, when would ancestor path ever get set? It
would seem that the client doesn't care about the ancestory -- that is only
important for the client to track when a "svn move" or "svn copy" is
performed (and then forgotten during the commit).

Given that the editor interface says the ancestor_revision is ignored when
the ancestor_path is NULL, then when/how does the checkout/update process
tell the WC what revision a particular file is?

thx,
-g

-- 
Greg Stein, http://www.lyra.org/