It's a desktop GUI for Git, along the same lines as Sourcetree. They've added stuff over time like various paid integrations and apparently a Kanban board, but

It's a desktop GUI for Git, along the same lines as Sourcetree. They've added stuff over time like various paid integrations and apparently a Kanban board, but it's always primarily been a Git GUI. Mailspring is another one I can think of. It's a free email client that offers extra features for pay.