Only call groupBy for actions that aren't filtered

[levilansing]

I'd like to propose a very small behavior change before the big 1.0:

Currently, groupBy is called for every action, even actions that are filtered. This change would only call groupBy when necessary, specifically, only for actions that are not filtered and will affect the history.

This is more of a logical/contractual change than anything else, but it would provide a small performance boost in the case of complex grouping logic. I'm proposing this change mainly because I was surprised groupBy was called for every action, and then I realized groupBy has no idea if the action was filtered or not, so I had to move some of my grouping logic into the filter option.

[omnidan]

thanks for the PR! looks good to me 😁