hack: add release generation script

with the introduction of carvel packaging[1], there'd be more complexity
added to the `make release` target that I believe is better to be
introduced to a bash script of its own rather than the Makefile.

this script then takes care of generating the contents of the `/release`
directory (gitignored) by preparing an `imgpkg` bundle[2] containing all
the relevant files for installing cartographer, as well as pushing that
bundle and then templating out the final package.

in the end, we have the following structure generated:

	./release/
	|
	├── cartographer.yaml		- installation for a `k apply -f-`
	|
	└── package			- installation via carvel pkging
	    ├── package-install.yaml
	    ├── package-metadata.yaml
	    └── package.yaml

[1]: https://carvel.dev/kapp-controller/docs/latest/packaging/
[2]: https://carvel.dev/imgpkg/docs/latest/

Signed-off-by: Ciro S. Costa <ciroscosta@vmware.com>

hack/release.sh

@@ -0,0 +1,118 @@
+#!/usr/bin/env bash
+# Copyright 2021 VMware
+#
+# 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 -o errexit
+set -o nounset
+set -o pipefail
+
+readonly ROOT=$(cd $(dirname $0)/.. && pwd)
+readonly SCRATCH=${SCRATCH:-$(mktemp -d)}
+readonly REGISTRY=${REGISTRY:-"$($ROOT/hack/ip.py):5000"}
+readonly BUNDLE=${BUNDLE:-$REGISTRY/cartographer-bundle}
+readonly RELEASE_VERSION=${RELEASE_VERSION:-"0.0.0-dev"}
+readonly RELEASE_DATE=${RELEASE_DATE:-$(date -Iseconds)}
+
+main() {
+        show_vars
+
+        cd $ROOT
+        create_imgpkg_bundle
+        generate_release
+}
+
+show_vars() {
+        echo "Vars:
+
+	BUNDLE:	       		$BUNDLE
+	REGISTRY:		$REGISTRY
+	RELEASE_DATE:		$RELEASE_DATE
+	RELEASE_VERSION:	$RELEASE_VERSION
+	ROOT:	       		$ROOT
+	SCRATCH:       		$SCRATCH
+	"
+}
+
+# creates, in a scratch location, an imgpkg bundle following the convention that
+# is expected of bundles for Packages (see ref):
+#
+#
+# 	.
+# 	├── bundle
+# 	│   ├── .imgpkg
+# 	│   │   └── images.yml			absolute image references to
+# 	│   │					images in this bundle
+# 	│   │
+# 	│   └── config
+# 	│       └── cartographer.yaml		everything from the release
+# 	│       │
+# 	│       └── overlays/			overlays to tweak properties
+# 	│                       		from the release according to
+# 	│                       		packaging configuration
+# 	│
+# 	└── bundle.lock.yaml			exact image reference to this
+# 						bundle
+#
+#
+# ref: https://carvel.dev/kapp-controller/docs/latest/packaging-artifact-formats/#package-contents-bundle
+#
+create_imgpkg_bundle() {
+        mkdir -p $SCRATCH/bundle/{.imgpkg,config}
+
+        cp -r ./packaging/{objects,overlays} $SCRATCH/bundle/config
+
+        ytt --ignore-unknown-comments -f ./config |
+                KO_DOCKER_REPO=$REGISTRY ko resolve -f- > \
+                        $SCRATCH/bundle/config/cartographer.yaml
+
+        kbld -f $SCRATCH/bundle/config/cartographer.yaml \
+                --imgpkg-lock-output $SCRATCH/bundle/.imgpkg/images.yml >/dev/null
+
+        imgpkg push -f $SCRATCH/bundle \
+                --bundle $BUNDLE \
+                --lock-output $SCRATCH/bundle.lock.yaml
+}
+
+# generates the final release directory containing the files that are meant to
+# be used during installation.
+#
+#
+# 	release
+# 	│
+# 	├── package
+# 	│   └── package-install.yaml
+# 	│   └── package-metadata.yaml
+# 	│   └── package.yaml
+# 	│
+# 	└── release.yaml
+#
+generate_release() {
+        local bundle_image=$(awk -F"image: " '{if ($2) print $2;}' $SCRATCH/bundle.lock.yaml)
+
+        rm -rf ./release
+        mkdir -p ./release/package
+
+        cp $SCRATCH/bundle/config/cartographer.yaml ./release
+        for package_fpath in ./packaging/package*.yaml; do
+                ytt --ignore-unknown-comments \
+                        -f ./packaging/values.yaml \
+                        -f $package_fpath \
+                        --data-value image=$bundle_image \
+                        --data-value releasedAt=$RELEASE_DATE \
+                        --data-value version=$RELEASE_VERSION > \
+                        ./release/package/$(basename $package_fpath)
+        done
+}
+
+main "$@"