Introduce GroupVersioner for capturing desired target version

Convert single GV and lists of GVs into an interface that can handle
more complex scenarios (everything internal, nothing supported). Pass
the interface down into conversion.

pkg/api/unversioned/group_version.go

@@ -179,6 +179,25 @@ func (gv GroupVersion) String() string {
 	return gv.Version
 }
 
+// KindForGroupVersionKinds identifies the preferred GroupVersionKind out of a list. It returns ok false
+// if none of the options match the group. It prefers a match to group and version over just group.
+// TODO: Move GroupVersion to a package under pkg/runtime, since it's used by scheme.
+// TODO: Introduce an adapter type between GroupVersion and runtime.GroupVersioner, and use LegacyCodec(GroupVersion)
+//   in fewer places.
+func (gv GroupVersion) KindForGroupVersionKinds(kinds []GroupVersionKind) (target GroupVersionKind, ok bool) {
+	for _, gvk := range kinds {
+		if gvk.Group == gv.Group && gvk.Version == gv.Version {
+			return gvk, true
+		}
+	}
+	for _, gvk := range kinds {
+		if gvk.Group == gv.Group {
+			return gv.WithKind(gvk.Kind), true
+		}
+	}
+	return GroupVersionKind{}, false
+}
+
 // ParseGroupVersion turns "group/version" string into a GroupVersion struct. It reports error
 // if it cannot parse the string.
 func ParseGroupVersion(gv string) (GroupVersion, error) {
@@ -241,6 +260,25 @@ func (gv *GroupVersion) UnmarshalText(value []byte) error {
 	return gv.unmarshal(value)
 }
 
+// GroupVersions can be used to represent a set of desired group versions.
+// TODO: Move GroupVersions to a package under pkg/runtime, since it's used by scheme.
+// TODO: Introduce an adapter type between GroupVersions and runtime.GroupVersioner, and use LegacyCodec(GroupVersion)
+//   in fewer places.
+type GroupVersions []GroupVersion
+
+// KindForGroupVersionKinds identifies the preferred GroupVersionKind out of a list. It returns ok false
+// if none of the options match the group.
+func (gvs GroupVersions) KindForGroupVersionKinds(kinds []GroupVersionKind) (target GroupVersionKind, ok bool) {
+	for _, gv := range gvs {
+		target, ok := gv.KindForGroupVersionKinds(kinds)
+		if !ok {
+			continue
+		}
+		return target, true
+	}
+	return GroupVersionKind{}, false
+}
+
 // ToAPIVersionAndKind is a convenience method for satisfying runtime.Object on types that
 // do not use TypeMeta.
 func (gvk *GroupVersionKind) ToAPIVersionAndKind() (string, string) {