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    FWIW GitLab uses a gRPC based solution (Gitaly) for all Git repository interactions, including Git wire protocol traffic (the Git protocol data is treated as a raw stream). See the protocol definition at https://gitlab.com/gitlab-org/gitaly/tree/master/proto. This allows GitLab to abstract the storage of Git repositories behind a gRPC interface.

    Fun fact: this is how Heptapod (https://foss.heptapod.net/heptapod/heptapod) - a fork of GitLab that supports Mercurial - works: they’ve taught Mercurial to answer the gRPC queries that Gitaly defines. GitLab issues gRPC requests and they are answered by Mercurial instead of Git. Most functionality “just works” and doesn’t care that Mercurial - not Git - is providing data. Abstractions and interfaces can be very powerful…

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      That’s interesting! I’ve looked at doing remote Git operations by creating an abstraction over the object store. The benefit is that the interface is much smaller than what you linked to. I guess the downside is higher latency for operations that need several round-trips. Do you know if that has been explored?

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        GitLab’s/Gitaly’s RPC protocol is massive. My understanding is they pretty much invent a specialized RPC method for every use case they have so they can avoid fragmented transactions, excessive round trips, etc. The RPC is completely internal to GitLab and doesn’t need to be backwards or forwards compatible over a long time horizon. So they can get away with high amounts of churn and experimentation. It’s a terrific solution for an internal RPC. That approach to protocol design won’t work for Git itself, however.