Fix image name parsing with tag and digest (#4406)

* Fix image name parsing with name and digest

Image names may contain both tag name and digest.  For example
`nginx:1.21.5@sha256:7826426c9d8d310c62fc68bcd5e8dde70cb39d4fbbd30eda3b1bd03e35fbde29`. Kustomizations with image transforms will not match
these image because the image parser assumes either a tag or digest, but not
both.

For a real life example of kuberenetes deployments that might need to perform
these types of transforms is from the [tekton-pipelines](https://github.com/tektoncd/pipeline) project (see the release.yaml).

* Return digest property from image name parser

image.Split now returns 3 fields: name, tag, and digest. The tag and digest
fields no longer include their respective delimiters (`:` and `@`).

* Fix merge file indentation

* Refactor imagetag updater string builder

api/filters/imagetag/imagetag_test.go

@@ -750,6 +750,96 @@ spec:
 				},
 			},
 		},
+		"image with tag and digest new name": {
+			input: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  image: nginx:1.2.1@sha256:46d5b90a7f4e9996351ad893a26bcbd27216676ad4d5316088ce351fb2c2c3dd
+`,
+			expectedOutput: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  image: apache:1.2.1@sha256:46d5b90a7f4e9996351ad893a26bcbd27216676ad4d5316088ce351fb2c2c3dd
+`,
+			filter: Filter{
+				ImageTag: types.Image{
+					Name:    "nginx",
+					NewName: "apache",
+				},
+			},
+			fsSlice: []types.FieldSpec{
+				{
+					Path: "spec/image",
+				},
+			},
+		},
+		"image with tag and digest new name new tag": {
+			input: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  image: nginx:1.2.1@sha256:46d5b90a7f4e9996351ad893a26bcbd27216676ad4d5316088ce351fb2c2c3dd
+`,
+			expectedOutput: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  image: apache:1.3.0
+`,
+			filter: Filter{
+				ImageTag: types.Image{
+					Name:    "nginx",
+					NewName: "apache",
+					NewTag:  "1.3.0",
+				},
+			},
+			fsSlice: []types.FieldSpec{
+				{
+					Path: "spec/image",
+				},
+			},
+		},
+		"image with tag and digest new name new tag and digest": {
+			input: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  image: nginx:1.2.1@sha256:46d5b90a7f4e9996351ad893a26bcbd27216676ad4d5316088ce351fb2c2c3dd
+`,
+			expectedOutput: `
+apiVersion: example.com/v1
+kind: Foo
+metadata:
+  name: instance
+spec:
+  image: apache:1.3.0@sha256:xyz
+`,
+			filter: Filter{
+				ImageTag: types.Image{
+					Name:    "nginx",
+					NewName: "apache",
+					NewTag:  "1.3.0",
+					Digest:  "sha256:xyz",
+				},
+			},
+			fsSlice: []types.FieldSpec{
+				{
+					Path: "spec/image",
+				},
+			},
+		},
 	}
 
 	for tn, tc := range testCases {

api/filters/imagetag/updater.go

@@ -30,18 +30,32 @@ func (u imageTagUpdater) SetImageValue(rn *yaml.RNode) error {
 		return nil
 	}
 
-	name, tag := image.Split(value)
+	name, tag, digest := image.Split(value)
 	if u.ImageTag.NewName != "" {
 		name = u.ImageTag.NewName
 	}
-	if u.ImageTag.NewTag != "" {
-		tag = ":" + u.ImageTag.NewTag
-	}
-	if u.ImageTag.Digest != "" {
-		tag = "@" + u.ImageTag.Digest
+
+	// overriding tag or digest will replace both original tag and digest values
+	if u.ImageTag.NewTag != "" && u.ImageTag.Digest != "" {
+		tag = u.ImageTag.NewTag
+		digest = u.ImageTag.Digest
+	} else if u.ImageTag.NewTag != "" {
+		tag = u.ImageTag.NewTag
+		digest = ""
+	} else if u.ImageTag.Digest != "" {
+		tag = ""
+		digest = u.ImageTag.Digest
 	}
 
-	return u.trackableSetter.SetScalar(name + tag)(rn)
+	// build final image name
+	if tag != "" {
+		name += ":" + tag
+	}
+	if digest != "" {
+		name += "@" + digest
+	}
+
+	return u.trackableSetter.SetScalar(name)(rn)
 }
 
 func (u imageTagUpdater) Filter(rn *yaml.RNode) (*yaml.RNode, error) {