small refector

Signed-off-by: Josh Dolitsky <jdolitsky@gmail.com>

pkg/registry/reference.go

@@ -26,6 +26,7 @@ import (
 
 var (
 	validPortRegEx     = regexp.MustCompile("^([1-9]\\d{0,3}|0|[1-5][0-9]{4}|6[0-4][0-9]{3}|65[0-4][0-9]{2}|655[0-2][0-9]|6553[0-5])$") // adapted from https://stackoverflow.com/a/12968117
+	emptyRepoError     = errors.New("parsed repo was empty")
 	tooManyColonsError = errors.New("ref may only contain a single colon character (:) unless specifying a port number")
 )
 
@@ -58,7 +59,7 @@ func ParseReference(s string) (*Reference, error) {
 	return &ref, nil
 }
 
-// setExtraFields adds the Rpeo and Tag fields to a Reference
+// setExtraFields adds the Repo and Tag fields to a Reference
 func (ref *Reference) setExtraFields() {
 	ref.Tag = ref.Object
 	ref.Repo = ref.Locator
@@ -92,22 +93,34 @@ func (ref *Reference) fixNoRepo() {
 
 // validate makes sure the ref meets our criteria
 func (ref *Reference) validate() error {
-	return ref.validateColons()
+	err := ref.validateRepo()
+	if err != nil {
+		return err
+	}
+	return ref.validateNumColons()
+}
+
+// validateRepo checks that the Repo field is non-empty
+func (ref *Reference) validateRepo() error {
+	if ref.Repo == "" {
+		return emptyRepoError
+	}
+	return nil
 }
 
-// validateColons verifies the ref only contains one colon max
-// (or two, there might be a port number specified i.e. :5000)
-func (ref *Reference) validateColons() error {
+// validateNumColon ensures the ref only contains a single colon character (:)
+// (or potentially two, there might be a port number specified i.e. :5000)
+func (ref *Reference) validateNumColons() error {
 	if strings.Contains(ref.Tag, ":") {
 		return tooManyColonsError
 	}
-	locParts := strings.Split(ref.Repo, ":")
-	locLastIndex := len(locParts) - 1
-	if 1 < locLastIndex {
+	parts := strings.Split(ref.Repo, ":")
+	lastIndex := len(parts) - 1
+	if 1 < lastIndex {
 		return tooManyColonsError
 	}
-	if 0 < locLastIndex {
-		port := strings.Split(locParts[locLastIndex], "/")[0]
+	if 0 < lastIndex {
+		port := strings.Split(parts[lastIndex], "/")[0]
 		if !isValidPort(port) {
 			return tooManyColonsError
 		}