I am currently using an MSYS2 installation instead of Git for Windows. I chose MSYS2 because it comes with pacman and am able to use other familiar tools like vim, awk and grep. I noticed that my MSYS2 startup is really slow. Googling it brought up the above link which explains the problem is a great detail and gives you a good solution. I am posting the link here for reference.

1. Create /etc/passwd and /etc/group
2. modify /etc/nsswitch.conf to use only file

This prevents MSYS2 to query Active Directory for login information.