Merge pull request #407 from tmc/fix-errhelp

flag: Emulate stdlib behavior and do not print ErrHelp

Author: tomasaschan

flag.go

@@ -1173,6 +1173,9 @@ func (f *FlagSet) Parse(arguments []string) error {
 		case ContinueOnError:
 			return err
 		case ExitOnError:
+			if err == ErrHelp {
+				os.Exit(0)
+			}
 			fmt.Fprintln(f.Output(), err)
 			os.Exit(2)
 		case PanicOnError: