Category Labels (RFC)

Needs comments / suggestions on how to handle regex labels for commitlog.

Currently the categorization works in the following way.

Eg: a catg regex like so would produce the labels
```sh
$ commitlog g --categories="feat:,fix:"
```

```md
## feat:
## fix:
```

Though this doesn't make sense when you have really complex regex's handling the categorisation.

So, there needs to be a way to create labels for these category regexes

One possible way is to change the way the flags are parsed and have more than one instance of the flag.
```sh
$ commitlog --category="Features%%feat:" --category="Fixes%%fix:"
```

Considering the chances of `%%` being together in a regex being very rare and also since the logic would only take the first separation to get the `LABEL` everything else would be compiled back as regex.

首先检查 --categories 选项背后的当前类别解析方式，并将其与提议的重复 --category 形式进行比较。定义应如何将标签与复杂正则表达式分隔开，然后验证对于简单模式和复杂模式，类别标题都能使用请求的标签生成。

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