m4_define(FMT_CODE, ⁨pre .code-sample {=
	m4_esyscmd(sed '
		s/[@\\}]/\\&/g
		m4_regexp($1, .*\.diff$,
			/^+/s/.*/@ins{-&}/
			/^-/s/.*/@del{-&}/
		)
		s/.*/@code{-&}/
	' $(dirname 'm4___file__')/$1)
}⁩)