cmd.Cmd completion fails in some cases, must allow the definition of readline completion delimiters

Bug report

Bug description:

cmd.Cmd does not allow the definition of readline completion delimiters, therefore, complete_*() methods will fail with completion options containing dashes (or other characters in readline's default list of delimiters).

Defining a Cmd.completer_delims (by default None) and then calling readline.set_completer_delims(self.completer_delims) (if Cmd.completer_delims is not None) after importing readline will do the trick.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

从 cmd.Cmd 的 completion 路径及其与 readline 的集成入手，重点关注当前如何选择 completion 分隔符。为包含短横线的 completion 选项添加回归测试，以确认可配置的分隔符行为；当这些选项能够成功完成，同时默认的分隔符行为保持不变时，即可完成。