support option for adding managed-by label

Makefile

@@ -198,7 +198,7 @@ build-kustomize-api: $(builtinplugins)
 
 .PHONY: test-unit-kustomize-api
 test-unit-kustomize-api: build-kustomize-api
-	cd api; go test ./...
+	cd api; go test ./...  -ldflags "-X sigs.k8s.io/kustomize/api/provenance.version=v444.333.222"
 
 .PHONY: test-unit-kustomize-plugins
 test-unit-kustomize-plugins:

api/krusty/kustomizer.go

@@ -4,6 +4,8 @@
 package krusty
 
 import (
+	"fmt"
+
 	"sigs.k8s.io/kustomize/api/builtins"
 	"sigs.k8s.io/kustomize/api/filesys"
 	"sigs.k8s.io/kustomize/api/internal/k8sdeps/transformer"
@@ -12,11 +14,16 @@ import (
 	"sigs.k8s.io/kustomize/api/k8sdeps/kunstruct"
 	"sigs.k8s.io/kustomize/api/k8sdeps/validator"
 	fLdr "sigs.k8s.io/kustomize/api/loader"
+	"sigs.k8s.io/kustomize/api/provenance"
 	"sigs.k8s.io/kustomize/api/resmap"
 	"sigs.k8s.io/kustomize/api/resource"
 	"sigs.k8s.io/kustomize/api/types"
 )
 
+const (
+	managedbyLabelKey = "app.kubernetes.io/managed-by"
+)
+
 // Kustomizer performs kustomizations.  It's meant to behave
 // similarly to the kustomize CLI, and can be used instead of
 // performing an exec to a kustomize CLI subprocess.
@@ -78,5 +85,15 @@ func (b *Kustomizer) Run(path string) (resmap.ResMap, error) {
 	if b.options.DoLegacyResourceSort {
 		builtins.NewLegacyOrderTransformerPlugin().Transform(m)
 	}
+	if b.options.AddManagedbyLabel {
+		t := builtins.LabelTransformerPlugin{
+			Labels: map[string]string{managedbyLabelKey: fmt.Sprintf("kustomize-%s", provenance.GetProvenance().Version)},
+			FieldSpecs: []types.FieldSpec{{
+				Path:               "metadata/labels",
+				CreateIfNotPresent: true,
+			}},
+		}
+		t.Transform(m)
+	}
 	return m, nil
 }

api/krusty/managedbylabel_test.go

@@ -0,0 +1,43 @@
+// Copyright 2020 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package krusty_test
+
+import (
+	"testing"
+
+	kusttest_test "sigs.k8s.io/kustomize/api/testutils/kusttest"
+)
+
+func TestAddManagedbyLabel(t *testing.T) {
+	th := kusttest_test.MakeHarness(t)
+	th.WriteF("/app/service.yaml", `
+apiVersion: v1
+kind: Service
+metadata:
+  name: myService
+spec:
+  ports:
+  - port: 7002
+`)
+	th.WriteK("/app", `
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+- service.yaml
+`)
+	options := th.MakeDefaultOptions()
+	options.AddManagedbyLabel = true
+	m := th.Run("/app", options)
+	th.AssertActualEqualsExpected(m, `
+apiVersion: v1
+kind: Service
+metadata:
+  labels:
+    app.kubernetes.io/managed-by: kustomize-v444.333.222
+  name: myService
+spec:
+  ports:
+  - port: 7002
+`)
+}

api/krusty/options.go

@@ -18,6 +18,11 @@ type Options struct {
 	// order as specified by the kustomization file(s).
 	DoLegacyResourceSort bool
 
+	// When true, a label
+	//     app.kubernetes.io/managed-by: kustomize-<version>
+	// is added to all the resources in the build out.
+	AddManagedbyLabel bool
+
 	// Restrictions on what can be loaded from the file system.
 	// See type definition.
 	LoadRestrictions types.LoadRestrictions