The requirement that patch sets don't break bisection can make things very hard on driver
Lets say I have replaced 30% of my driver code with newer, better code.
It's extremely hard to break the changes into separate patches that are
logically separate, so that they can be reviewed one one hand, and on the other, none of them
break anything, so bisection works.
Maybe the way to solve this is to have bisection by patch-sets rather than by individual