[sujal-maheshwari2004]

What was wrong

buf lint exited 100 on main because DiffPromptResponse is the response of both DiffPrompt and DiffCommits:

$ buf lint
proto\priompt\v1\prompt.proto:14:3:"priompt.v1.DiffPromptResponse" is used as the request or response type for multiple RPCs.
proto\priompt\v1\prompt.proto:28:3:"priompt.v1.DiffPromptResponse" is used as the request or response type for multiple RPCs.
proto\priompt\v1\prompt.proto:28:48:RPC response type "DiffPromptResponse" should be named "DiffCommitsResponse" or "PromptServiceDiffCommitsResponse".
exit=100

The fix

I kept the shared type and added targeted // buf:lint:ignore comments on the two RPCs (RPC_REQUEST_RESPONSE_UNIQUE on both, RPC_RESPONSE_STANDARD_NAME on DiffCommits), with a one-line reason.

I also tried the other option the issue mentions, a dedicated DiffCommitsResponse { repeated Change changes = 1; }. It is wire-compatible, but:

• it changes the Go API: the server's DiffCommits(...) (*pb.DiffPromptResponse, error) and its shared diff() helper would stop compiling on the next proto bump.
• buf breaking (FILE rules) rejects it:

  prompt.proto:33:48:RPC "DiffCommits" on service "PromptService" changed response type from "priompt.v1.DiffPromptResponse" to "priompt.v1.DiffCommitsResponse".
  alt breaking exit=100
  

With the lint exception, wire format and the Go API stay the same. Regenerated stubs (pinned protocolbuffers/go:v1.36.12, grpc/go:v1.6.2, which match the committed headers) differ only in doc comments in prompt_grpc.pb.go. prompt.pb.go is byte-identical.

CI gets a new buf job that runs buf lint.

Evidence

$ buf lint                                   -> exit 0
$ buf breaking --against '.git#branch=origin/main'  -> exit 0
$ GOWORK=off go build ./... && go vet ./... && go test ./...
ok  github.com/priompt/proto/semdiff
ok  github.com/priompt/proto/validate

Fixes #3

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