aptitude: upgrading only necessary stable-to-testing.

[Sthu Deus <sthu.deus@gmail.com>]

Good day.

I have mixed system: stable & testing. On

# aptitude full-upgrade

I often have a situation when a stable status packages needs to be
upgraded up to testing status because of dependency (as I do
understand that: when a testing status package being upgraded and in
order it needs more fresh version (from testing) of a stable status
package), but aptitude does not so - but rather offers diver mysterious
solutions - anything but upgrading the package on dependency from its
stable to testing status.

My question is what and where should I specify in its configuration so
that it would include in its decision making - upgrading to testing
status as well? - NOT that it will upgrade every stable package to
testing, but only those without which - because of dependency - it is
impossibly to upgrade others.

Thank You for Your time.