Refactor bool_flag into sub pkg

pkg/util/flag/tristate.go

@@ -0,0 +1,83 @@
+/*
+Copyright 2014 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 flag
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// Tristate is a flag compatible with flags and pflags that
+// keeps track of whether it had a value supplied or not.
+type Tristate int
+
+const (
+	Unset Tristate = iota // 0
+	True
+	False
+)
+
+func (f *Tristate) Default(value bool) {
+	*f = triFromBool(value)
+}
+
+func (f Tristate) String() string {
+	b := boolFromTri(f)
+	return fmt.Sprintf("%t", b)
+}
+
+func (f Tristate) Value() bool {
+	b := boolFromTri(f)
+	return b
+}
+
+func (f *Tristate) Set(value string) error {
+	boolVal, err := strconv.ParseBool(value)
+	if err != nil {
+		return err
+	}
+
+	*f = triFromBool(boolVal)
+	return nil
+}
+
+func (f Tristate) Provided() bool {
+	if f != Unset {
+		return true
+	}
+	return false
+}
+
+func (f *Tristate) Type() string {
+	return "tristate"
+}
+
+func boolFromTri(t Tristate) bool {
+	if t == True {
+		return true
+	} else {
+		return false
+	}
+}
+
+func triFromBool(b bool) Tristate {
+	if b {
+		return True
+	} else {
+		return False
+	}
+}