diff --git a/internal/tool/tool.go b/internal/tool/tool.go
new file mode 100644
index 0000000000..d21a099803
--- /dev/null
+++ b/internal/tool/tool.go
@@ -0,0 +1,196 @@
+// Copyright 2018 The Go 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 tool is an opinionated harness for writing Go tools.
+package tool
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"reflect"
+	"runtime"
+	"runtime/pprof"
+	"runtime/trace"
+	"time"
+)
+
+// This file is a very opinionated harness for writing your main function.
+// The original version of the file is in golang.org/x/tools/internal/tool.
+//
+// It adds a method to the Application type
+//     Main(name, usage string, args []string)
+// which should normally be invoked from a true main as follows:
+//     func main() {
+//       (&Application{}).Main("myapp", "non-flag-command-line-arg-help", os.Args[1:])
+//     }
+// It recursively scans the application object for fields with a tag containing
+//     `flag:"flagname" help:"short help text"``
+// uses all those fields to build command line flags.
+// It expects the Application type to have a method
+//     Run(context.Context, args...string) error
+// which it invokes only after all command line flag processing has been finished.
+// If Run returns an error, the error will be printed to stderr and the
+// application will quit with a non zero exit status.
+
+// Profile can be embedded in your application struct to automatically
+// add command line arguments and handling for the common profiling methods.
+type Profile struct {
+	CPU    string `flag:"profile.cpu" help:"write CPU profile to this file"`
+	Memory string `flag:"profile.mem" help:"write memory profile to this file"`
+	Trace  string `flag:"profile.trace" help:"write trace log to this file"`
+}
+
+// Application is the interface that must be satisfied by an object passed to Main.
+type Application interface {
+	// Name returns the application's name. It is used in help and error messages.
+	Name() string
+	// Most of the help usage is automatically generated, this string should only
+	// describe the contents of non flag arguments.
+	Usage() string
+	// ShortHelp returns the one line overview of the command.
+	ShortHelp() string
+	// DetailedHelp should print a detailed help message. It will only ever be shown
+	// when the ShortHelp is also printed, so there is no need to duplicate
+	// anything from there.
+	// It is passed the flag set so it can print the default values of the flags.
+	// It should use the flag sets configured Output to write the help to.
+	DetailedHelp(*flag.FlagSet)
+	// Run is invoked after all flag processing, and inside the profiling and
+	// error handling harness.
+	Run(ctx context.Context, args ...string) error
+}
+
+// This is the type returned by CommandLineErrorf, which causes the outer main
+// to trigger printing of the command line help.
+type commandLineError string
+
+func (e commandLineError) Error() string { return string(e) }
+
+// CommandLineErrorf is like fmt.Errorf except that it returns a value that
+// triggers printing of the command line help.
+// In general you should use this when generating command line validation errors.
+func CommandLineErrorf(message string, args ...interface{}) error {
+	return commandLineError(fmt.Sprintf(message, args...))
+}
+
+// Main should be invoked directly by main function.
+// It will only return if there was no error.
+func Main(ctx context.Context, app Application, args []string) {
+	s := flag.NewFlagSet(app.Name(), flag.ExitOnError)
+	s.Usage = func() {
+		fmt.Fprint(s.Output(), app.ShortHelp())
+		fmt.Fprintf(s.Output(), "\n\nUsage: %v [flags] %v\n", app.Name(), app.Usage())
+		app.DetailedHelp(s)
+	}
+	p := addFlags(s, reflect.StructField{}, reflect.ValueOf(app))
+	s.Parse(args)
+	err := func() error {
+		if p != nil && p.CPU != "" {
+			f, err := os.Create(p.CPU)
+			if err != nil {
+				return err
+			}
+			if err := pprof.StartCPUProfile(f); err != nil {
+				return err
+			}
+			defer pprof.StopCPUProfile()
+		}
+
+		if p != nil && p.Trace != "" {
+			f, err := os.Create(p.Trace)
+			if err != nil {
+				return err
+			}
+			if err := trace.Start(f); err != nil {
+				return err
+			}
+			defer func() {
+				trace.Stop()
+				log.Printf("To view the trace, run:\n$ go tool trace view %s", p.Trace)
+			}()
+		}
+
+		if p != nil && p.Memory != "" {
+			f, err := os.Create(p.Memory)
+			if err != nil {
+				return err
+			}
+			defer func() {
+				runtime.GC() // get up-to-date statistics
+				if err := pprof.WriteHeapProfile(f); err != nil {
+					log.Printf("Writing memory profile: %v", err)
+				}
+				f.Close()
+			}()
+		}
+		return app.Run(ctx, s.Args()...)
+	}()
+	if err != nil {
+		fmt.Fprintf(s.Output(), "%s: %v\n", app.Name(), err)
+		if _, printHelp := err.(commandLineError); printHelp {
+			s.Usage()
+		}
+		os.Exit(2)
+	}
+}
+
+// addFlags scans fields of structs recursively to find things with flag tags
+// and add them to the flag set.
+func addFlags(f *flag.FlagSet, field reflect.StructField, value reflect.Value) *Profile {
+	// is it a field we are allowed to reflect on?
+	if field.PkgPath != "" {
+		return nil
+	}
+	// now see if is actually a flag
+	flagName, isFlag := field.Tag.Lookup("flag")
+	help := field.Tag.Get("help")
+	if !isFlag {
+		// not a flag, but it might be a struct with flags in it
+		if value.Elem().Kind() != reflect.Struct {
+			return nil
+		}
+		p, _ := value.Interface().(*Profile)
+		// go through all the fields of the struct
+		sv := value.Elem()
+		for i := 0; i < sv.Type().NumField(); i++ {
+			child := sv.Type().Field(i)
+			v := sv.Field(i)
+			// make sure we have a pointer
+			if v.Kind() != reflect.Ptr {
+				v = v.Addr()
+			}
+			// check if that field is a flag or contains flags
+			if fp := addFlags(f, child, v); fp != nil {
+				p = fp
+			}
+		}
+		return p
+	}
+	switch v := value.Interface().(type) {
+	case flag.Value:
+		f.Var(v, flagName, help)
+	case *bool:
+		f.BoolVar(v, flagName, *v, help)
+	case *time.Duration:
+		f.DurationVar(v, flagName, *v, help)
+	case *float64:
+		f.Float64Var(v, flagName, *v, help)
+	case *int64:
+		f.Int64Var(v, flagName, *v, help)
+	case *int:
+		f.IntVar(v, flagName, *v, help)
+	case *string:
+		f.StringVar(v, flagName, *v, help)
+	case *uint:
+		f.UintVar(v, flagName, *v, help)
+	case *uint64:
+		f.Uint64Var(v, flagName, *v, help)
+	default:
+		log.Fatalf("Cannot understand flag of type %T", v)
+	}
+	return nil
+}