::fixture-ready::
$ find source backup -type f | sort
backup/.snapshot
backup/app/config.yml
backup/content/index.md
backup/old-report.csv
backup/tmp/empty.cache
source/app/config.yml
source/assets/logo.svg
source/content/about.md
source/content/index.md
::exit-code::0
$ comm -3 <(find source -type f | sed 's#^source/##' | sort) <(find backup -type f | sed 's#^backup/##' | sort)
	.snapshot
assets/logo.svg
content/about.md
	old-report.csv
	tmp/empty.cache
::exit-code::0