Merge pull request #53 from choria-io/52

(#52) improve handling of duplicate command errors

app.go

@@ -906,7 +906,7 @@ func (a *Application) MustParseWithUsage(args []string) (command string) {
 		fmt.Fprintf(a.errorWriter, "error: %v, use --help for full help including flags and arguments\n\n", err)
 		ut = a.errorUsageTemplate
 
-	case errorIs(err, ErrRequiredArgument, ErrRequiredFlag, ErrUnknownLongFlag, ErrUnknownShortFlag, ErrExpectedFlagArgument, ErrFlagCannotRepeat, ErrUnexpectedArgument):
+	case errorIs(err, ErrRequiredArgument, ErrRequiredFlag, ErrUnknownLongFlag, ErrUnknownShortFlag, ErrExpectedFlagArgument, ErrFlagCannotRepeat, ErrUnexpectedArgument, ErrDuplicateCommand):
 		fmt.Fprintf(a.errorWriter, "error: %v\n\n", err)
 
 	default:

cmd.go

@@ -196,7 +196,7 @@ func (c *cmdGroup) init() error {
 			defaults = append(defaults, cmd.name)
 		}
 		if seen[cmd.name] {
-			return fmt.Errorf("duplicate command %q", cmd.name)
+			return fmt.Errorf("%w %q", ErrDuplicateCommand, cmd.name)
 		}
 		seen[cmd.name] = true
 		for _, alias := range cmd.aliases {

errors.go

@@ -35,4 +35,7 @@ var (
 
 	// ErrUnexpectedArgument indicates an unexpected argument was encountered
 	ErrUnexpectedArgument = errors.New("unexpected argument")
+
+	// ErrDuplicateCommand indicates that a command was defined multiple times
+	ErrDuplicateCommand = errors.New("duplicate command")
 )