Sanitize image names before deciding what to load

I was able to reproduce the issue locally and work out a fix. I'd be
happy for feedback on whether I've chosen the right place to fix it.

When determining which images to sideload (for kind and k3d), we compare
`localImages` and `deployerImages`. The former from `skaffold.yaml`, and
the latter from Kubernetes manifest files. The image names from
Kubernetes manifests are sanitized in
`pkg/skaffold/kubernetes/manifests/images.go#L51` (and `L113`) in the
call to docker.ParseReference.

The same doesn't happen to image names from `skaffold.yaml`. This change
sanitizes these image names just for determining whether to sideload the
images.

In other parts of the code we look up image pipelines from
`skaffold.yaml` using the image name, so I was hesitant to change how
`localImages` is used (with 'raw' image names).

The hypothesis from the previous commit is disproven, so I'm
adding back the `sha256` tag policy in the custom builder example. To
make the test case easier to identify from the build logs, I renamed the
pod in the custom builder example.

New hypothesis: Could this be related to the issues some users are
reporting with images not being sideloaded when using Helm? E.g., #5159

integration/examples/custom/k8s/pod.yaml

@@ -1,8 +1,8 @@
 apiVersion: v1
 kind: Pod
 metadata:
-  name: getting-started
+  name: getting-started-custom
 spec:
   containers:
-  - name: getting-started
-    image: github.com/googlecontainertools/skaffold/examples/custom
+  - name: getting-started-custom
+    image: ko://github.com/GoogleContainerTools/skaffold/examples/custom

integration/examples/custom/skaffold.yaml

@@ -9,3 +9,5 @@ build:
         paths:
         - "go.mod"
         - "**.go"
+  tagPolicy:
+    sha256: {}

integration/run_test.go

@@ -113,7 +113,7 @@ var tests = []struct {
 	{
 		description: "custom builder",
 		dir:         "examples/custom",
-		pods:        []string{"getting-started"},
+		pods:        []string{"getting-started-custom"},
 	},
 	{
 		description: "buildpacks Go",

pkg/skaffold/kubernetes/loader/load.go

@@ -28,6 +28,7 @@ import (
 	"k8s.io/client-go/tools/clientcmd/api"
 
 	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/config"
+	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/docker"
 	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/graph"
 	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/kubectl"
 	kubectx "github.com/GoogleContainerTools/skaffold/pkg/skaffold/kubernetes/context"
@@ -60,7 +61,7 @@ func NewImageLoader(kubeContext string, cli *kubectl.CLI) *ImageLoader {
 func imagesToLoad(localImages, deployerImages, images []graph.Artifact) []graph.Artifact {
 	local := map[string]bool{}
 	for _, image := range localImages {
-		local[image.ImageName] = true
+		local[docker.SanitizeImageName(image.ImageName)] = true
 	}
 
 	tracked := map[string]bool{}
@@ -72,7 +73,7 @@ func imagesToLoad(localImages, deployerImages, images []graph.Artifact) []graph.
 
 	var res []graph.Artifact
 	for _, image := range images {
-		if tracked[image.ImageName] {
+		if tracked[docker.SanitizeImageName(image.ImageName)] {
 			res = append(res, image)
 		}
 	}

pkg/skaffold/kubernetes/loader/load_test.go

@@ -200,6 +200,13 @@ func TestImagesToLoad(t *testing.T) {
 			builtImages:    []graph.Artifact{{ImageName: "image1", Tag: "foo"}},
 			expectedImages: nil,
 		},
+		{
+			name:           "single image marked as local, with ko prefix and Go import path with uppercase characters",
+			localImages:    []graph.Artifact{{ImageName: "ko://example.com/Organization/Image1", Tag: "Foo"}},
+			deployerImages: []graph.Artifact{{ImageName: "example.com/organization/image1", Tag: "Foo"}},
+			builtImages:    []graph.Artifact{{ImageName: "ko://example.com/Organization/Image1", Tag: "Foo"}},
+			expectedImages: []graph.Artifact{{ImageName: "ko://example.com/Organization/Image1", Tag: "Foo"}},
+		},
 		{
 			name:           "two images marked as local",
 			localImages:    []graph.Artifact{{ImageName: "image1", Tag: "foo"}, {ImageName: "image2", Tag: "bar"}},