Commit after unstaging a new book does not trigger rebuild

[cderv]

See this https://github.com/rstudio/bookdown.org/commit/3376eba050ac015f41c08696cfdff3c8b97403f1

It is possible that this is a limitation where a commit / push by another workflow does not trigger a push even for another workflow. We could probably call / trigger the event from within the workflow instead.