Add gemini-agent Prow plugin

Implements a Prow plugin triggered by /gemini-agent <task> comments
on GitHub issues and PRs. The plugin collects GitHub context (issue metadata,
PR diffs, recent comments) and sends it to Gemini on Vertex AI for analysis.

Assisted by Opus 4.6

Signed-off-by: Arnaud Meukam <ameukam@gmail.com>

Author: ameukam

go.mod

@@ -67,6 +67,7 @@ require (
 	golang.org/x/time v0.12.0
 	gomodules.xyz/jsonpatch/v2 v2.5.0
 	google.golang.org/api v0.233.0
+	google.golang.org/genai v1.57.0
 	google.golang.org/genproto v0.0.0-20250303144028-a0af3efb3deb
 	google.golang.org/genproto/googleapis/api v0.0.0-20251202230838-ff82c1b0f217
 	google.golang.org/grpc v1.79.3

go.sum

@@ -1020,6 +1020,8 @@ google.golang.org/appengine v1.6.1/go.mod h1:i06prIuMbXzDqacNJfV5OdTW448YApPu5ww
 google.golang.org/appengine v1.6.5/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
 google.golang.org/appengine v1.6.6/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
 google.golang.org/appengine v1.6.7/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
+google.golang.org/genai v1.57.0 h1:qTyG2ynz5dQy2jF4CvZdLHHVslhR0heMue+zM1a4GNM=
+google.golang.org/genai v1.57.0/go.mod h1:A3kkl0nyBjyFlNjgxIwKq70julKbIxpSxqKO5gw/gmk=
 google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
 google.golang.org/genproto v0.0.0-20190307195333-5fe7a883aa19/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
 google.golang.org/genproto v0.0.0-20190418145605-e7d98fc518a7/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=

pkg/hook/plugin-imports/plugin-imports.go

@@ -19,6 +19,7 @@ package pluginimports
 // We need to empty import all enabled plugins so that they will be linked into
 // any hook binary.
 import (
+	_ "sigs.k8s.io/prow/pkg/plugins/geminiagent"
 	_ "sigs.k8s.io/prow/pkg/plugins/approve" // Import all enabled plugins.
 	_ "sigs.k8s.io/prow/pkg/plugins/assign"
 	_ "sigs.k8s.io/prow/pkg/plugins/blockade"

pkg/plugins/config.go

@@ -97,6 +97,22 @@ type Configuration struct {
 	Welcome              []Welcome                    `json:"welcome,omitempty"`
 	Override             Override                     `json:"override,omitempty"`
 	Help                 Help                         `json:"help,omitempty"`
+
+	// GeminiAgents holds per-repo configuration for the gemini-agent plugin.
+	GeminiAgents []GeminiAgentConfig `json:"gemini_agents,omitempty"`
+}
+
+// GeminiAgentConfig holds per-repo settings for the gemini-agent plugin.
+type GeminiAgentConfig struct {
+	// Repos is either of the form org/repos or just org.
+	Repos []string `json:"repos,omitempty"`
+
+	// Model is the Gemini model to use (e.g. "gemini-3-flash-preview").
+	Model string `json:"model,omitempty"`
+
+	// AllowedTeams is a list of GitHub team slugs whose members are allowed
+	// to invoke /gemini-agent, in addition to standard trigger trust.
+	AllowedTeams []string `json:"allowed_teams,omitempty"`
 }
 
 type Help struct {