Add oc image append which adds layers to a schema1/2 image

This command can take zero or more gzipped layer tars (in Docker layer
format) and append them to an existing image or a scratch image and then
push the new image to a registry. Layers in the existing image are
pushed as well. The caller can mutate the provided config as it goes.

pkg/image/apis/image/docker10/conversion.go

@@ -0,0 +1,24 @@
+package docker10
+
+// Convert_DockerV1CompatibilityImage_to_DockerImageConfig takes a Docker registry digest
+// (schema 2.1) and converts it to the external API version of Image.
+func Convert_DockerV1CompatibilityImage_to_DockerImageConfig(in *DockerV1CompatibilityImage, out *DockerImageConfig) error {
+	*out = DockerImageConfig{
+		ID:              in.ID,
+		Parent:          in.Parent,
+		Comment:         in.Comment,
+		Created:         in.Created,
+		Container:       in.Container,
+		DockerVersion:   in.DockerVersion,
+		Author:          in.Author,
+		Architecture:    in.Architecture,
+		Size:            in.Size,
+		OS:              "linux",
+		ContainerConfig: in.ContainerConfig,
+	}
+	if in.Config != nil {
+		out.Config = &DockerConfig{}
+		*out.Config = *in.Config
+	}
+	return nil
+}