The first lines of code I wrote for Codebase were for a local proxy server to serve as a remote for Git to interface with 
I moved on from that once http_request seemed viable.
In addition to helping with authentication there are some other benefits to having a local server such as it being a mechanism to address certain concerns, e.g. limitations with HTTP uploads that sounded like they might get addressed with the help of boundary nodes
There’s definitely a trade-off though; it’s more work for myself and for end users.
With some insight from @domwoe I think Codebase can easily support verifying signed commits. That doesn’t help with authentication in general though.