Fix infinite loop flag parsing with short options

parse.go

@@ -22,28 +22,27 @@ func parseIter(set *flag.FlagSet, ip iterativeParser, args []string) error {
 		}
 
 		errStr := err.Error()
-		trimmed := strings.TrimPrefix(errStr, "flag provided but not defined: ")
+		trimmed := strings.TrimPrefix(errStr, "flag provided but not defined: -")
 		if errStr == trimmed {
 			return err
 		}
 
 		// regenerate the initial args with the split short opts
-		newArgs := []string{}
 		for i, arg := range args {
-			if arg != trimmed {
-				newArgs = append(newArgs, arg)
+			// skip args that are not part of the error message
+			if name := strings.TrimLeft(arg, "-"); name != trimmed {
 				continue
 			}
 
-			shortOpts := splitShortOptions(set, trimmed)
+			// if we can't split, the error was accurate
+			shortOpts := splitShortOptions(set, arg)
 			if len(shortOpts) == 1 {
 				return err
 			}
 
-			// add each short option and all remaining arguments
-			newArgs = append(newArgs, shortOpts...)
-			newArgs = append(newArgs, args[i+1:]...)
-			args = newArgs
+			// swap current argument with the split version
+			args = append(args[:i], append(shortOpts, args[i+1:]...)...)
+			break
 		}
 
 		// Since custom parsing failed, replace the flag set before retrying