Add beginnings of new cr command

go/src/infra/tools/cr/lib/terminal/terminal.go

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package terminal provides utilities for printing to and reading user input
+// from an interactive terminal.
+package terminal
+
+import (
+        "bufio"
+        "fmt"
+        "os"
+)
+
+var showDebug = false
+
+func ToggleDebug() {
+        showDebug = !showDebug
+}
+
+func SetDebug(show bool) {
+        showDebug = show
+}
+
+func Print(format string, args ...interface{}) {
+        fmt.Printf(format, args)
+}
+
+func Debug(format string, args ...interface{}) {
+        if showDebug {
+                fmt.Printf(format, args)
+        }
+}
+
+func Prompt(prompt string) string {
+        fmt.Print(prompt)
+        reader := bufio.NewReader(os.Stdin)
+        text, _ := reader.ReadString('\n')
+        return text
+}