code: public CommandLine setAtFileCommentChar(Character atFileCommentChar) {
          getCommandSpec().parser().atFileCommentChar(atFileCommentChar);
          for (CommandLine command : getCommandSpec().subcommands().values()) {
              command.setAtFileCommentChar(atFileCommentChar);
          }
          return this;
      }
docs: Sets the character that starts a single-line comment or {@code null} if all content of argument files should
  be interpreted as arguments (without comments).
  If specified, all characters from the comment character to the end of the line are ignored.
  @param atFileCommentChar the character that starts a single-line comment or {@code null}. The default is {@code '#'}.
  @return this {@code CommandLine} object, to allow method chaining
  @since 3.5