In the global settings, add action buttons to register (and unregister) the following menu items in the OS file explorer's right click context menu.

1. "Open with SourceGit" - Enabled only if the folder is a valid git repo. Opens the folder as a new tab or an existing tab.
2. "Git Clone" - Enabled only if the folder is not a valid git repo. Triggers the "Clone Remote Repository" dialog, and open as new tab after the clone finishes

In Linux, there may be a lot of different desktop environments and file managers.
But for Windows, I think it's relatively easy to start this feature with.