So this means that cannot contain `,`?  E.g., let's say that I want to color the pattern `/foo,bar/`.  How would I do that with this code?

This won't work; it looks like that will cause the pattern to be interpreted as `foo` and the color as `bar`:
```
... | highlight --filter=foo,bar
```

Worse, because the `--filter` code and the "legacy" argument handling has been unified, that means that this has the same problem:
```
... | highlight --color=red foo,bar
```