Unpublish pages with page-unpublish AsciiDoc attribute set
If a page sets the page-unpublish
AsciiDoc attribute in the document header (technically called a page attribute in this case), Antora should not publish that page. While a page can be unpublished by prefixing the filename with an underscore (e.g., _hidden.adoc), this feature would allow this behavior to be controlled conditionally without having to rename the file.
While this is possible to achieve using an Antora extension, it's common enough to provide support for it out of the box.
Antora also has a better opportunity at present to unpublish the page without allowing references to that page to be resolved. That's because, internally, Antora extracts the AsciiDoc metadata from each page before converting the pages, so no xrefs will yet be resolved. (In the future, Antora may emit a new event at this transition point).