Is it better to leave the unfilled items empty or commented out? I'd like this to work out of the box as well as possible if someone forgets to customize it. CC @matthewfeickert.

Is it better to leave the unfilled items empty or commented out?

I would be inclined to say that if it doesn't pass pipx run cffconvert --validate that is a problem. Empty entries will automatically fail validation and commented out entries aren't much better as you still need to have a minimum viable spec. In my mind this means that it should either be customized as part of setup or that it should be left as a suggestion but not an automatic part of cookie.

cffconvert offers a validate-cff pre-commit hook: https://github.com/citation-file-format/cffconvert/blob/main/.pre-commit-hooks.yaml

@henryiii Would it be OK for me to help move forward the two CFF PRs and also add documentation about what a CITATION.cff file does and how to set up the Zenodo-GitHub integration to automatically generate DOIs? Since these haven't had activity since 2022 I want to check what's up before I start :)

Docs for sure. The problem with adding this by default is that a user has to configure it to use it, a partial file isn't helpful and not everyone wants or knows to set it up. What I'd really like is support for a check boxes in cookiecutter and copier, then we could provide a list of optional features to enable.

support for a check boxes in cookiecutter and copier

Fairly sure we can have a boolean answer in copier that we can use to create or not create file, is that what you mean?

Yes, but I'd like a series of these, and having to answer for each one is less ideal than a list of checkboxes. But having a "Include citation file?" is probably the right way to go for now.