I have found articles regarding how to install Git on a Windows server and use SSH (such as CopSSH) for authentication. I am a little surprised by this as I remember readin
You can use Windows Credential Store for Git https://gitcredentialstore.codeplex.com/
It saves your Git credentials in your PC's Windows Credential Store, keeping it safe in a secure location. And it's really easy to use :)
Gitlab Enterprise claims to support Active Directory. I haven't demo'd it yet, but I'm considering it as an option as we migrate a svn server that our organization wants to have AD backing it.
You can also host the repo with IIS over HTTPS and then protect each project subfolder with Windows user credentials.
Git Credential Manager for Windows is officially supported by Microsoft to use Windows authentication to authenticate yourself to git.
https://github.com/Microsoft/Git-Credential-Manager-for-Windows
You can simply use a shared folder as git repository inside your domain and administer it with your domain users.
c:/> git clone \\myserver\repository\myfolder
You could use scm-manager, which has an active directory plugin.