Adjust "diff-pr.sh" to ignore "COPY --from=" (since it cannot reasonably access files from the referenced image/stage context)

diff-pr.sh

@@ -167,6 +167,9 @@ copy-tar() {
 			$(awk '
 				toupper($1) == "COPY" || toupper($1) == "ADD" {
 					for (i = 2; i < NF; i++) {
+						if ($i ~ /^--from=/) {
+							next
+						}
 						if ($i !~ /^--chown=/) {
 							print $i
 						}