By the way, why would you change your passport if it is still valid till August? Secondly, wasn't it possible to extend it? or are the pages finished? It all depends which Country's passport you hold.
NB, I think both copies of the passport are needed especially if you will have to proof that you have resided in such and such Countries.
It's only my own opinion, Wait for someone to give his/her own idea
If you are currently in process of filling your application, then mention your latest passport details (i.e. New Passport). But if you have already filled your application with passport details which stands cancel now (after new passport issued to you) then please inform your visa office with change of passport details.
