commands: Extract some common types into its own file

See #4598

commands/hugo.go

@@ -1,4 +1,4 @@
-// Copyright 2016 The Hugo Authors. All rights reserved.
+// Copyright 2018 The Hugo 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.
@@ -59,13 +59,6 @@ import (
 // provide a cleaner external API, but until then, this is it.
 var Hugo *hugolib.HugoSites
 
-const (
-	ansiEsc    = "\u001B"
-	clearLine  = "\r\033[K"
-	hideCursor = ansiEsc + "[?25l"
-	showCursor = ansiEsc + "[?25h"
-)
-
 // Reset resets Hugo ready for a new full build. This is mainly only useful
 // for benchmark testing etc. via the CLI commands.
 func Reset() error {
@@ -73,45 +66,6 @@ func Reset() error {
 	return nil
 }
 
-// commandError is an error used to signal different error situations in command handling.
-type commandError struct {
-	s         string
-	userError bool
-}
-
-func (c commandError) Error() string {
-	return c.s
-}
-
-func (c commandError) isUserError() bool {
-	return c.userError
-}
-
-func newUserError(a ...interface{}) commandError {
-	return commandError{s: fmt.Sprintln(a...), userError: true}
-}
-
-func newSystemError(a ...interface{}) commandError {
-	return commandError{s: fmt.Sprintln(a...), userError: false}
-}
-
-func newSystemErrorF(format string, a ...interface{}) commandError {
-	return commandError{s: fmt.Sprintf(format, a...), userError: false}
-}
-
-// Catch some of the obvious user errors from Cobra.
-// We don't want to show the usage message for every error.
-// The below may be to generic. Time will show.
-var userErrorRegexp = regexp.MustCompile("argument|flag|shorthand")
-
-func isUserError(err error) bool {
-	if cErr, ok := err.(commandError); ok && cErr.isUserError() {
-		return true
-	}
-
-	return userErrorRegexp.MatchString(err.Error())
-}
-
 // HugoCmd is Hugo's root command.
 // Every other command attached to HugoCmd is a child command to it.
 var HugoCmd = &cobra.Command{