Use Go tools to gather license files

Issue: [ch11840]
See: 02f2c25

Makefile

@@ -158,7 +158,7 @@ endif
 
 pgo-base: pgo-base-$(IMGBUILDER)
 
-pgo-base-build: $(PGOROOT)/build/pgo-base/Dockerfile
+pgo-base-build: $(PGOROOT)/build/pgo-base/Dockerfile licenses
 	$(IMGCMDSTEM) \
 		-f $(PGOROOT)/build/pgo-base/Dockerfile \
 		-t $(PGO_IMAGE_PREFIX)/pgo-base:$(PGO_IMAGE_TAG) \
@@ -258,3 +258,8 @@ generate-rbac:
 hack/tools/envtest: SHELL = bash
 hack/tools/envtest:
 	source '$(shell $(GO) list -f '{{ .Dir }}' -m 'sigs.k8s.io/controller-runtime')/hack/setup-envtest.sh' && fetch_envtest_tools $@
+
+.PHONY: license licenses
+license: licenses
+licenses:
+	./bin/license_aggregator.sh ./cmd/...

bin/license_aggregator.sh

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+
+# Copyright 2021 Crunchy Data Solutions, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -eu
+
+# Inputs / outputs
+IN_PACKAGES=("$@")
+OUT_DIR=licenses
+
+# Clean up before we start our work
+rm -rf ${OUT_DIR:?}/*/
+
+# Download dependencies of the requested packages, excluding the main module.
+# - https://golang.org/ref/mod#glos-main-module
+module=$(go list -m)
+modules=$(go list -deps -f '{{with .Module}}{{.Path}}{{"\t"}}{{.Dir}}{{end}}' "${IN_PACKAGES[@]}")
+dependencies=$(grep -v "^${module}" <<< "${modules}")
+
+while IFS=$'\t' read -r module directory; do
+	licenses=$(find "${directory}" -type f -ipath '*license*' -not -name '*.go')
+	[ -n "${licenses}" ] || continue
+
+	while IFS= read -r license; do
+		# Replace the local module directory with the module path.
+		# - https://golang.org/ref/mod#module-path
+		relative="${module}${license:${#directory}}"
+
+		# Copy the license file with the same layout as the module.
+		destination="${OUT_DIR}/${relative%/*}"
+		install -d "${destination}"
+		install -m 0644 "${license}" "${destination}"
+	done <<< "${licenses}"
+done <<< "${dependencies}"

build/pgo-base/Dockerfile

@@ -18,7 +18,6 @@ LABEL vendor="Crunchy Data" \
 	io.openshift.tags="postgresql,postgres,sql,nosql,crunchy" \
 	io.k8s.description="Trusted open source PostgreSQL-as-a-Service"
 
-COPY redhat/licenses /licenses
 COPY redhat/atomic/help.1 /help.1
 COPY redhat/atomic/help.md /help.md
 COPY licenses /licenses

licenses/.gitignore

@@ -0,0 +1 @@
+*