* add tests for the --postcss option in the new CLI
* add `oneOf` ability to the `arg()` functionality
By default, `arg()` doesn't have a way to define multiple types. We want
the possibility of using `--postcss` (Boolean) or `--postcss
./custom-path.js`. But by default this is not possible.
This commit will allow us to do a few things, mainly:
- Keep the same API using the `{ type: oneOf(String, Boolean), description: '...' }`
- Keep the `--help` output similar
What we did behind the scenes is make sure to put the non recognized
flags in the `_` arguments list. This is possible by doing `permissive:
true`. We then manually parse those and resolve the correct value.
* ensure that we can use a custom `--postcss ./with-custom-path.js`
f4799a32e8