Recoving branch point tag?

[Roy Smith]

Imagine I've got module foo which I've branched at tag X, and I
branch off that in turn by doing something like:

cvs get -r X foo
cd foo
cvs tag -b Y
cvs update -r Y

I do some work in the sandbox, commit the files, then blow away the
sandbox.  Is it now possible, from looking at the logs, to recover the
information that X is the base of the Y branch?

For a given file, it's easy to see the branching structure with
respect to revision numbers.  But, each file in the module will have
its own set of revision numbers, and there can be many tags which
correspond to a given revision.  My suspicion is that the information
I seek is not recoverable from the data stored in the repository.  Am
I right?

I guess this is one of the things subversion will address?