Continuing the discussion from What's your blogdown workflow to include work from other projects
Also, the SO question on the matter is posted here: https://stackoverflow.com/questions/50750447/netlify-fails-to-deploy-site-after-public-is-added-to-gitignore

Some extra facts (not in SO question):
What triggered it: an attempt to stop building my site locally (i.e. clearing git cache and adding public and blogdown to .gitignore). Also documented in this SO question: https://stackoverflow.com/questions/50750447/netlify-fails-to-deploy-site-after-public-is-added-to-gitignore