[css-nesting-1] Indenting of deeply nested rules is still only one level

[sesse]

There's an example from the nesting-parsing.html test:

main { & > section, & > article { & > header { color: green; } } }

As far as I understand the algorithm (which is defined in https://drafts.csswg.org/cssom-1/#serialize-a-css-rule, I believe—it seems to have been updated for nesting, and then a near-identical copy was pasted into the css-nesting-1 draft for CSSNestingRule), this should be serialized as:

main {
  & > section, & > article {
  & > header { color: green; }
}
}

This isn't optimal, by any stretch; not only is it hard to understand the nesting level of the innermost rule, but the second-to-last } also comes at an unexpected place. Could we perhaps have some sort of explicit string replacement? Or idea of nesting level? I don't know how these algorithms are usually defined to be as implementable as possible.

[tabatkins]

Yes, the serialization algo for rules has been incredibly busted (not technically broken, just producing terrible output) for many, many years. You get the same result for nesting @media/@support/style rules today.

So this ends up being a dupe of #4828