Remove unnecessary CentOS references and add Kibana's timestamp-ignoring code

Author: tianon

.github/workflows/history.sh

@@ -6,16 +6,12 @@ set -Eeuo pipefail
 docker image history --no-trunc --format '{{ .CreatedBy }}' "$@" \
 	| tac \
 	| sed -r 's!^/bin/sh[[:space:]]+-c[[:space:]]+(#[(]nop[)][[:space:]]+)?!!' \
-	| awk '
-		# ignore the first ADD of the base image (base image changes unnecessarily break our diffs)
-		NR == 1 && $1 == "ADD" && $4 == "/" { next }
-		# TODO consider instead just removing the checksum in $3
+	| gawk '
+		# munge the checksum of the first ADD of the base image (base image changes unnecessarily break our diffs)
+		NR == 1 && $1 == "ADD" && $4 == "/" { $2 = "-" }
 
-		# ignore obviously "centos" LABEL instructions (include a timestamp, so base image changes unnecessarily break our diffs)
-		$1 == "LABEL" && / org.opencontainers.image.vendor=CentOS | org.label-schema.vendor=CentOS / { next }
-
-		# just ignore the default CentOS CMD value (not relevant to our needs)
-		$0 == "CMD [\"/bin/bash\"]" { next }
+		# remove "org.label-schema.build-date" and "org.opencontainers.image.created" (https://github.com/elastic/dockerfiles/pull/101#pullrequestreview-879623350)
+		$1 == "LABEL" { gsub(/ (org[.]label-schema[.]build-date|org[.]opencontainers[.]image[.]created)=[^ ]+( [0-9:+-]+)?/, "") }
 
 		# in logstash, Elastic builds pull artifacts from "http://localhost:8000" instead of "https://artifacts.elastic.co/downloads/logstash"
 		/localhost:8000\/logstash/ { gsub(/http:\/\/localhost:8000\/logstash/, "https://artifacts.elastic.co/downloads/logstash/logstash") }