I see what you are saying, although once through the garage door opening the garage opens out so shouldn't be a problem but maybe mindful for others, although if the garage was that narrow im not sure how anyone would get out and squeeze down the gap to exit the garage on foot?
I have a similar issue with my garage. I've just measured it. Placing a ruler against the door frame it sticks out 21cm with the mirror folded up. I have to fold them to get it in. I ask my wife to ensure I'm central. I haven't run her over yet. She has also made some nice ear warmers from some old leather to ensure there are no scrapes they are very useful.
Or you can hang 2 tennisballs with ropes from the ceiling and drive in between them. People sometimes hang a tennisball from garage ceiling that touches windscreen when car is about the hit back wall when parking sensors did not yet exist.