add http head based digest comparison to avoid dockerhub rate limits

pkg/registry/helpers/helpers.go

@@ -0,0 +1,36 @@
+package helpers
+
+import (
+	"fmt"
+	url2 "net/url"
+)
+
+// ConvertToHostname strips a url from everything but the hostname part
+func ConvertToHostname(url string) (string, string, error) {
+	urlWithSchema := fmt.Sprintf("x://%s", url)
+	u, err := url2.Parse(urlWithSchema)
+	if err != nil {
+		return "", "", err
+	}
+	hostName := u.Hostname()
+	port := u.Port()
+
+	return hostName, port, err
+}
+
+// NormalizeRegistry makes sure variations of DockerHubs registry
+func NormalizeRegistry(registry string) (string, error) {
+	hostName, port, err := ConvertToHostname(registry)
+	if err != nil {
+		return "", err
+	}
+
+	if hostName == "registry-1.docker.io" || hostName == "docker.io" {
+		hostName = "index.docker.io"
+	}
+
+	if port != "" {
+		return fmt.Sprintf("%s:%s", hostName, port), nil
+	}
+	return hostName, nil
+}

pkg/registry/helpers/helpers_test.go

@@ -0,0 +1,31 @@
+package helpers
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"testing"
+)
+
+func TestHelpers(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Helper Suite")
+}
+
+var _ = Describe("the helpers", func() {
+
+	When("converting an url to a hostname", func() {
+		It("should return docker.io given docker.io/containrrr/watchtower:latest", func() {
+			host, port, err := ConvertToHostname("docker.io/containrrr/watchtower:latest")
+			Expect(err).NotTo(HaveOccurred())
+			Expect(host).To(Equal("docker.io"))
+			Expect(port).To(BeEmpty())
+		})
+	})
+	When("normalizing the registry information", func() {
+		It("should return index.docker.io given docker.io", func() {
+			out, err := NormalizeRegistry("docker.io/containrrr/watchtower:latest")
+			Expect(err).NotTo(HaveOccurred())
+			Expect(out).To(Equal("index.docker.io"))
+		})
+	})
+})