This represents the future direction of protobuf, replacing proto2/proto3 syntax with editions. These will enable more incremental evolution of protobuf APIs through features, which are individual behaviors (such as whether field presence is explicit or implicit). For more details see https://protobuf.dev/editions/overview/.
This PR contains a working implementation of editions for the protoc frontend and C++ code generation, along with various infrastructure improvements to support it. It gives early access for anyone who wants to a preview of editions, but has no effect on proto2/proto3 syntax. It is flag-guarded behind the `--experimental_editions` flag, and is an experimental feature with no guarantees.
PiperOrigin-RevId: 544805690
Mike Kruskal