Move kubeconfig utility to a shared pkg

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

internal/kubeconfig/currentcontext_test.go

@@ -0,0 +1,55 @@
+package kubeconfig
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestKubeconfig_GetCurrentContext(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`current-context: foo`)}
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	v := kc.GetCurrentContext()
+
+	expected := "foo"
+	if v != expected {
+		t.Fatalf("expected=%q; got=%q", expected, v)
+	}
+}
+
+func TestKubeconfig_GetCurrentContext_missingField(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`abc: def`)}
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	v := kc.GetCurrentContext()
+
+	expected := ""
+	if v != expected {
+		t.Fatalf("expected=%q; got=%q", expected, v)
+	}
+}
+
+func TestKubeconfig_UnsetCurrentContext(t *testing.T) {
+	tl := &testLoader{in: strings.NewReader(`current-context: foo`)}
+	kc := new(Kubeconfig).WithLoader(tl)
+	if err := kc.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	if err := kc.UnsetCurrentContext(); err != nil {
+		t.Fatal(err)
+	}
+	if err := kc.Save(); err != nil {
+		t.Fatal(err)
+	}
+
+	out := tl.out.String()
+	expected := `current-context: ""
+`
+	if out != expected {
+		t.Fatalf("expected=%q; got=%q", expected, out)
+	}
+}