::fixture-ready::
$ grep -Rni --include='*.html' 'rel="canonical"' public
public/draft.html:5:<link rel="canonical" href="https://example.com/draft.html">
public/blog/post.html:4:<link rel="canonical" href="https://example.com/blog/post.html">
public/index.html:5:<link rel="canonical" href="https://example.com/">
::exit-code::0
$ find public -name '*.html' -print | while read -r f; do grep -qi 'rel="canonical"' "$f" || echo "$f"; done
public/about.html
::exit-code::0