Support kubectl group/resource name

pkg/api/latest/latest.go

@@ -37,6 +37,8 @@ var (
 	// AllPreferredGroupVersions returns the preferred versions of all
 	// registered groups in the form of "group1/version1,group2/version2,..."
 	AllPreferredGroupVersions = allGroups.AllPreferredGroupVersions
+	// IsRegistered is a shortcut to allGroups.IsRegistered.
+	IsRegistered = allGroups.IsRegistered
 )
 
 // GroupMetaMap is a map between group names and their metadata.
@@ -65,6 +67,12 @@ func (g GroupMetaMap) Group(group string) (*GroupMeta, error) {
 	return groupMeta, nil
 }
 
+// IsRegistered takes a string and determines if it's one of the registered groups
+func (g GroupMetaMap) IsRegistered(group string) bool {
+	_, found := g[group]
+	return found
+}
+
 // TODO: This is an expedient function, because we don't check if a Group is
 // supported throughout the code base. We will abandon this function and
 // checking the error returned by the Group() function.