Small performance issues

[ma2ciek]

There's a noticeable delay after pressing enter and waiting for the prompt. I've checked and on my machine the scripts needs ~80-90ms to run on average mainly due to synchronously spawned child processes.

I've tried to change the logic to more asynchronous, but running few git tasks in parallel didn't helped me much, I was able to cut off only ~10-15ms of the script execution time. I've been thinking also about some kind of server running in the background and updating only changed parts of the prompt, but this would be hard to implement and maintain.