API extension for Git hashes

[oreiche]

The Justbuild authors recently published a modified version of the API, with improvements for Git-specific use cases. @sluongng suggested to open an issue to discuss whether the API could be further improved in this regard.

Justbuild already implements this extended API, both server and client side. It's specification can be found here: https://github.com/just-buildsystem/justbuild/blob/master/doc/specification/remote-protocol.org
This document also discusses the improvements introduced by this change.

Oliver

[asartori86]

It would be great to have a proper enum for this hashing strategy #257