Move extensions.LabelSelector to unversioned.

Move type LabelSelector and type LabelSelectorRequirement from pkg/apis/extensions
This avoids an import loop when Job (and later DaemonSet, Deployment, ReplicaSet)
are moved out of extensions to new api groups.

Also Move LabelSelectorAsSelector utility from pkg/apis/extensions/ to pkg/api/unversioned/
Also its test.
Also LabelSelectorOp* constants.
Also the pkg/apis/extensions/validation functions ValidateLabelSelectorRequirement and
ValidateLabelSelector move to pkg/api/unversioned

The related type in pkg/apis/extensions/v1beta1/ is staying there.  I might move
it in another PR if neccessary.

pkg/api/unversioned/helpers_test.go

@@ -0,0 +1,83 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+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 unversioned
+
+import (
+	"reflect"
+	"testing"
+
+	"k8s.io/kubernetes/pkg/labels"
+)
+
+func TestLabelSelectorAsSelector(t *testing.T) {
+	matchLabels := map[string]string{"foo": "bar"}
+	matchExpressions := []LabelSelectorRequirement{{
+		Key:      "baz",
+		Operator: LabelSelectorOpIn,
+		Values:   []string{"qux", "norf"},
+	}}
+	mustParse := func(s string) labels.Selector {
+		out, e := labels.Parse(s)
+		if e != nil {
+			panic(e)
+		}
+		return out
+	}
+	tc := []struct {
+		in        *LabelSelector
+		out       labels.Selector
+		expectErr bool
+	}{
+		{in: nil, out: labels.Nothing()},
+		{in: &LabelSelector{}, out: labels.Everything()},
+		{
+			in:  &LabelSelector{MatchLabels: matchLabels},
+			out: mustParse("foo in (bar)"),
+		},
+		{
+			in:  &LabelSelector{MatchExpressions: matchExpressions},
+			out: mustParse("baz in (norf,qux)"),
+		},
+		{
+			in:  &LabelSelector{MatchLabels: matchLabels, MatchExpressions: matchExpressions},
+			out: mustParse("foo in (bar),baz in (norf,qux)"),
+		},
+		{
+			in: &LabelSelector{
+				MatchExpressions: []LabelSelectorRequirement{{
+					Key:      "baz",
+					Operator: LabelSelectorOpExists,
+					Values:   []string{"qux", "norf"},
+				}},
+			},
+			expectErr: true,
+		},
+	}
+
+	for i, tc := range tc {
+		out, err := LabelSelectorAsSelector(tc.in)
+		if err == nil && tc.expectErr {
+			t.Errorf("[%v]expected error but got none.", i)
+		}
+		if err != nil && !tc.expectErr {
+			t.Errorf("[%v]did not expect error but got: %v", i, err)
+		}
+		if !reflect.DeepEqual(out, tc.out) {
+			t.Errorf("[%v]expected:\n\t%+v\nbut got:\n\t%+v", i, tc.out, out)
+		}
+	}
+}