a fast and friendly git client for Mac and Windows
Fork has quickly become my go-to GUI tool for working with git on macOS. They also offer a Windows build, but I have not yet given it a try.
I do not preform all my git operations through Fork. For instance, fetch, push, pull and rebase operations I still preform with the standard git CLI. However, when I need to view branches or the git history, I have found Fork to be an invaluable replacement for the likes of SourceTree and GitKraken. Another alternative I briefly explored was Tower, however it's $69 per year price tag placed it out of my acceptable range for a tool that I only partially rely on (for my work involving git).
My two drawbacks about Fork are that it has an unknown future (the developers have not promised that it will be offered for free forever) and that the development of it is done as closed-source. That being said, it is still my top pick for a git GUI application.