I seem to recall there being some discussion (I can't remember the
specific cases) about whether it would be sensible to have, for at least
the first release after a split, all the new packages depending on the
thinned down base one.
As an example, someone using git-cvs currently would only have the git
package. If we list git-cvs as a requirement for the new git package,
when they upgrade git they'll automatically get git-cvs and won't lose
any functionality. The following update can lose the git-cvs
requirement, giving the full advantage of the separated packages.