Add protocol buffer generation automation to maintain sync with upstream Kubernetes

[Copilot]

Protocol buffer files were manually maintained and became outdated, missing fields like resources in V1.PodSpec that exist in both upstream Kubernetes proto definitions and OpenAPI-generated models.

Changes

Automation Script

• scripts/update-proto.sh: Generates proto files from kubernetes-client/gen, parameterized by KUBERNETES_BRANCH environment variable

CI/CD Integration

• .github/workflows/generate.yml: Added "Generate Proto" step between OpenAPI generation and patches, using same Kubernetes branch parameter

Documentation

• proto/README.md: Documents automated workflow trigger and manual script usage

Generated Files

• Regenerated all 37 proto files from upstream Kubernetes master branch

Result

// Previously failed - resources field was missing
V1.PodSpec podSpec = V1.PodSpec.newBuilder()
    .setResources(V1.ResourceRequirements.newBuilder()
        .putLimits("cpu", quantity)
        .build())
    .build();

// Now works - field 40 present with proper accessors
podSpec.hasResources();    // ✓
podSpec.getResources();    // ✓

Proto and OpenAPI models now maintain consistency automatically on each generation run.

Warning

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• repository.sonatype.org
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java -classpath /home/REDACTED/work/java/java/.mvn/wrapper/maven-wrapper.jar -Dmaven.multiModuleProjectDirectory=/home/REDACTED/work/java/java org.apache.maven.wrapper.MavenWrapperMain clean compile -pl proto -am (dns block)

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Protocol Buffer support needs automation to keep it in sync.</issue_title>
<issue_description>Describe the bug
The generated protobuf specification is inconsistent with the non protobuf classes.
The resources field is missing from the

V1.PodSpec.newBuilder()
   .addResource(...) //missing

class V1PodSpec{
    @SerializedName("resources")
    @Nullable
    private V1ResourceRequirements resources;
}

original golang specification

// +featureGate=PodLevelResources
	// +optional
	Resources *ResourceRequirements `json:"resources,omitempty" protobuf:"bytes,40,opt,name=resources"`

To Reproduce
Observe the generated protobuf code
https://github.com/kubernetes-client/java/raw/refs/tags/v25.0.0/proto/src/main/java/io/kubernetes/client/proto/V1.java

vs

https://github.com/kubernetes-client/java/blob/v25.0.0/kubernetes/src/main/java/io/kubernetes/client/openapi/models/V1PodSpec.java

Expected behavior
The resource shall be present in the protobuf variant too
</issue_description>

<agent_instructions>Please add automation similar to the generate automation for generating new code, but instead generate protocol buffers. You should use the https://github.com/kubernetes-client/gen repository.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Protocol Buffer support needs automation to keep it in sync. #4367

---

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[brendandburns]

/ok-to-test

[brendandburns]

/lgtm
/approve

[brendandburns]

/lgtm
/approve

[k8s-ci-robot]

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