[client-go] Polymorphic Scale Client

This introduces a polymorphic scale client capable of operating against
scale subresources which return different group-versions of Scale.  The
scale subresources may be in group-versions different than the scale
itself, so that we no longer need a copy of every scalable resource in
the extensions API group.

To discovery which Scale group-versions go to which subresources,
discovery is used.

The scale client maintains its own internal versions and conversions to
several external versions, with a "hub" version that's a copy of the
autoscaling internal version.

It currently supports the following group-versions for Scale subresources:

- extensions/v1beta1.Scale
- autoscaling/v1.Scale

Kubernetes-commit: d61a2d90372c301dd11088df8941acf2bb01c38c

scale/scheme/extensionsint/BUILD

@@ -0,0 +1,31 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "doc.go",
+        "register.go",
+    ],
+    importpath = "k8s.io/client-go/scale/scheme/extensionsint",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//vendor/k8s.io/api/extensions/v1beta1:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
+        "//vendor/k8s.io/client-go/scale/scheme:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

scale/scheme/extensionsint/doc.go

@@ -0,0 +1,22 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package extensionsint contains the necessary scaffolding of the
+// internal version of extensions as required by conversion logic.
+// It doesn't have any of its own types -- it's just necessary to
+// get the expected behavoir out of runtime.Scheme.ConvertToVersion
+// and associated methods.
+package extensionsint

scale/scheme/extensionsint/register.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package extensionsint
+
+import (
+	extensionsv1beta1 "k8s.io/api/extensions/v1beta1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	scalescheme "k8s.io/client-go/scale/scheme"
+)
+
+// GroupName is the group name use in this package
+const GroupName = extensionsv1beta1.GroupName
+
+// SchemeGroupVersion is group version used to register these objects
+var SchemeGroupVersion = schema.GroupVersion{Group: GroupName, Version: runtime.APIVersionInternal}
+
+// Kind takes an unqualified kind and returns a Group qualified GroupKind
+func Kind(kind string) schema.GroupKind {
+	return SchemeGroupVersion.WithKind(kind).GroupKind()
+}
+
+// Resource takes an unqualified resource and returns a Group qualified GroupResource
+func Resource(resource string) schema.GroupResource {
+	return SchemeGroupVersion.WithResource(resource).GroupResource()
+}
+
+var (
+	SchemeBuilder = runtime.NewSchemeBuilder(addKnownTypes)
+	AddToScheme   = SchemeBuilder.AddToScheme
+)
+
+// Adds the list of known types to api.Scheme.
+func addKnownTypes(scheme *runtime.Scheme) error {
+	scheme.AddKnownTypes(SchemeGroupVersion,
+		&scalescheme.Scale{},
+	)
+	return nil
+}