If you're in this situation, just connect your generator to your house wiring with your suicide lead.
Oh wait, you mean your generator's in your garage too? Bugger.
I had a similar situation recently when I had a blown circuit breaker. I can lift my door up a few inches and fish out a wire which is connected to the release lever (roller door).
You should be able to put an external manual release on at least one of those doors.
Another option for you is to not have a permanent battery but to put a permanent connection external to your garage so you can just connect up your car to provide temporary power.
Personally, I'm planning to cut a door into my breezeblocks and enable pedestrian access that way.