Preserve line-end comments when replacing image

Previously: replace the YNode (yaml.Node) with a new one which is just
the replacement string.
Now: change the value of the YNode, and set it back in place.

controllers/testdata/appconfig-expected/deploy.yaml

@@ -7,4 +7,4 @@ spec:
     spec:
       containers:
       - name: hello
-        image: helloworld:1.0.1
+        image: helloworld:1.0.1 # SETTER_SITE

controllers/testdata/appconfig-expected2/deploy.yaml

@@ -7,4 +7,4 @@ spec:
     spec:
       containers:
       - name: hello
-        image: helloworld:1.2.0
+        image: helloworld:1.2.0 # SETTER_SITE

controllers/testdata/appconfig/deploy.yaml

@@ -7,4 +7,4 @@ spec:
     spec:
       containers:
       - name: hello
-        image: helloworld:1.0.0
+        image: helloworld:1.0.0 # SETTER_SITE

pkg/update/testdata/replace/commented-expected/deployment.yaml

@@ -0,0 +1,11 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: foo
+  namespace: bar
+spec:
+  template:
+    spec:
+      containers:
+      - name: c
+        image: used:v1.1.0 # the comment must stay!

pkg/update/testdata/replace/commented/deployment.yaml

@@ -0,0 +1,11 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: foo
+  namespace: bar
+spec:
+  template:
+    spec:
+      containers:
+      - name: c
+        image: used:v1.0.0 # the comment must stay!

pkg/update/update.go

@@ -36,7 +36,6 @@ func makeUpdateImagesFilter(originalRepo, replacement string) kio.Filter {
 	}
 
 	canonName := originalRef.Context().String()
-	replacementNode := yaml.NewScalarRNode(replacement)
 
 	replaceContainerImage := func(container *yaml.RNode) error {
 		if imageField := container.Field("image"); imageField != nil {
@@ -45,7 +44,9 @@ func makeUpdateImagesFilter(originalRepo, replacement string) kio.Filter {
 				return err
 			}
 			if ref.Context().String() == canonName {
-				imageField.Value.SetYNode(replacementNode.YNode())
+				ynode := imageField.Value.YNode()
+				ynode.Value = replacement
+				imageField.Value.SetYNode(ynode)
 			}
 		}
 		return nil

pkg/update/update_test.go

@@ -32,4 +32,12 @@ var _ = Describe("Update image everywhere", func() {
 		Expect(UpdateImageEverywhere("testdata/replace/original", tmp, "used", "used:v1.1.0")).To(Succeed())
 		test.ExpectMatchingDirectories("testdata/replace/expected", tmp)
 	})
+
+	It("keeps comments intact", func() {
+		tmp, err := ioutil.TempDir("", "gotest")
+		Expect(err).ToNot(HaveOccurred())
+		defer os.RemoveAll(tmp)
+		Expect(UpdateImageEverywhere("testdata/replace/commented", tmp, "used", "used:v1.1.0")).To(Succeed())
+		test.ExpectMatchingDirectories("testdata/replace/commented-expected", tmp)
+	})
 })