Actually it might require the gitlens extension. It's very well integrated and I've been using it for so long I don't know where one ends and the other begins.

Actually it might require the gitlens extension. It's very well integrated and I've been using it for so long I don't know where one ends and the other begins. Regardless, if you open the diff view, the right hand side is editable and you can make selections like any other view.