add docker image search api

Signed-off-by: soulseen <sunzhu@yunify.com>

pkg/models/registries/manifest_test.go

@@ -0,0 +1,31 @@
+package registries
+
+import (
+	"testing"
+)
+
+func TestDigestFromDockerHub(t *testing.T) {
+
+	testImage := Image{Domain: "docker.io", Path: "library/alpine", Tag: "latest"}
+	r, err := CreateRegistryClient("", "", "docker.io")
+	if err != nil {
+		t.Fatalf("Could not get client: %s", err)
+	}
+
+	digestUrl := r.GetDigestUrl(testImage)
+
+	// Get token.
+	token, err := r.Token(digestUrl)
+	if err != nil || token == "" {
+		t.Fatalf("Could not get token: %s", err)
+	}
+
+	d, err, _ := r.ImageManifest(testImage, token)
+	if err != nil {
+		t.Fatalf("Could not get digest: %s", err)
+	}
+
+	if d == nil {
+		t.Error("Empty digest received")
+	}
+}