Allows to use versions like 1.6.4 instead v1.6.4

cmd/kubeadm/app/util/version.go

@@ -26,7 +26,7 @@ import (
 
 var (
 	kubeReleaseBucketURL  = "https://storage.googleapis.com/kubernetes-release/release"
-	kubeReleaseRegex      = regexp.MustCompile(`^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)([-0-9a-zA-Z_\.+]*)?$`)
+	kubeReleaseRegex      = regexp.MustCompile(`^v?(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)([-0-9a-zA-Z_\.+]*)?$`)
 	kubeReleaseLabelRegex = regexp.MustCompile(`^[[:lower:]]+(-[-\w_\.]+)?$`)
 )
 
@@ -49,7 +49,10 @@ var (
 //  latest-1.0  (and similarly 1.1, 1.2, 1.3, ...)
 func KubernetesReleaseVersion(version string) (string, error) {
 	if kubeReleaseRegex.MatchString(version) {
-		return version, nil
+		if strings.HasPrefix(version, "v") {
+			return version, nil
+		}
+		return "v" + version, nil
 	} else if kubeReleaseLabelRegex.MatchString(version) {
 		url := fmt.Sprintf("%s/%s.txt", kubeReleaseBucketURL, version)
 		resp, err := http.Get(url)

cmd/kubeadm/app/util/version_test.go

@@ -45,6 +45,7 @@ func TestValidVersion(t *testing.T) {
 		"v1.6.0-alpha.0.536+d60d9f3269288f",
 		"v1.5.0-alpha.0.1078+1044b6822497da-pull",
 		"v1.5.0-alpha.1.822+49b9e32fad9f32-pull-gke-gci",
+		"v1.6.1_coreos.0",
 	}
 	for _, s := range validVersions {
 		ver, err := KubernetesReleaseVersion(s)
@@ -61,8 +62,9 @@ func TestValidVersion(t *testing.T) {
 func TestInvalidVersion(t *testing.T) {
 	invalidVersions := []string{
 		"v1.3",
-		"1.4.0",
-		"1.4.5+git",
+		"1.4",
+		"b1.4.0",
+		"c1.4.5+git",
 		"something1.2",
 	}
 	for _, s := range invalidVersions {
@@ -77,6 +79,24 @@ func TestInvalidVersion(t *testing.T) {
 	}
 }
 
+func TestValidConvenientForUserVersion(t *testing.T) {
+	validVersions := []string{
+		"1.4.0",
+		"1.4.5+git",
+		"1.6.1_coreos.0",
+	}
+	for _, s := range validVersions {
+		ver, err := KubernetesReleaseVersion(s)
+		t.Log("Valid: ", s, ver, err)
+		if err != nil {
+			t.Errorf("KubernetesReleaseVersion unexpected error for version %q: %v", s, err)
+		}
+		if ver != "v"+s {
+			t.Errorf("KubernetesReleaseVersion should return semantic version string. %q vs. %q", s, ver)
+		}
+	}
+}
+
 func TestVersionFromNetwork(t *testing.T) {
 	type T struct {
 		Content       string