Using dash "-" to define stdout not working

**Issue by [TheDeadCode](https://github.com/TheDeadCode)**
_Saturday Aug 05, 2017 at 18:08 GMT_
_Originally opened as https://github.com/gsscoder/commandline/issues/466_

----

A bit like wget where you can do `wget https://someurl -O -` to say to output to stdout.
Although I cannot get it to work:

```
./generator.exe -o -

ERROR(S):
Option 'o, output' has no value.
Required option 'o, output' is missing.
```

重現報告中的 `./generator.exe -o -` 呼叫，並將其與文件所述的輸出選項行為進行比較。追蹤命令列剖析器如何將單獨的連字號作為選項值處理，然後為輸出至 stdout 新增測試涵蓋率，並確認不再發生必要選項錯誤。

由索引模型根據 Issue 內容生成。