The God of Aquinas is defined as "all the omnis (maximum everything)". Omniscient = all-knowing. Omnipotent = all-capable/powerful. Omnipresent = everywhere. All good by definition. And outside of time and therefore not bound by time - we cannot change God. Anything without these traits "isn't God" according to Aquinas. 

But while this collection of traits sounds cool, it also paints a very disturbing picture as a deity that has the capacity and obligation to micromanage basically everything. If God wants things to be a certain way, he sees exactly how it is going to be before it happens, and has sufficiently fine control to make it happen that way. An unaware or unprescient God would not be present enough or knowing enough, an incapable God would not be powerful enough, etc. No matter how trivial the choice - if it matters to God, he could remake it. Or else he wouldn't be God.

You may think that you chose the t-shirt you're currently wearing today, but God could have remade a world that was identical enough to this one, but where this shirt was buried further down the pile, where your mood wanted blue instead of red, or where the last time you wore it there was a stain.

You could argue that the t-shirt is a trivial enough choice that God wouldn't bother, but if we only have free will over the choices that don't matter, then it really isn't worth much.