I added logic to mine to check for a .noprompt file and disable the git part of my bash prompt as I generally want it enabled, but a few large repos are too slow with it. You could do something similar, I'm sure.
I wonder if an asynchronous approach could be implemented. Like starting the git status and the likes in a separate process and killing it after a certain timeout if it takes too long.
While I like that there is a .noprompt feature it's mainly a workaround. Maybe there could be a toggle feature where the user can turn on and off the git prompt on demand, wouldn't be hard to implement.
Maybe I will start hacking on it, I have some ideas to optimize it further.
https://github.com/xtrementl/dev-bash-git-ps1
I wonder if this one is any faster. Waiting for a bash prompt in large repos can be frustrating.