add kubectl-cnpg package (#179)

The CloudNativePG kubectl plugin is not packaged, so hosts have no supported way to install it. kubectl only completes plugin args via a `kubectl_complete-<plugin>` helper on PATH. Needs unkin/terraform-artifactapi#50 applied for the download to pass the github remote allowlist.

- add `kubectl-cnpg` 1.30.1 for almalinux/el9 and fedora 42/43/44
- fetch the tarball via the artifactapi github remote and verify it against upstream checksums
- ship `kubectl_complete-cnpg` for `kubectl cnpg` completion
- ship bash/zsh/fish completions generated at build time

Reviewed-on: #179
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

rpms/kubectl-cnpg/metadata.yaml

@@ -0,0 +1,22 @@
+name: kubectl-cnpg
+github: cloudnative-pg/cloudnative-pg
+description: CloudNativePG kubectl plugin.
+arch: amd64
+platform: linux
+maintainer: The CloudNativePG Contributors
+homepage: https://github.com/cloudnative-pg/cloudnative-pg
+license: Apache-2.0
+dist_tag: true
+builds:
+- repository:
+  - almalinux/el9
+  image: git.unkin.net/unkin/almalinux9-rpmbuilder:latest
+  release: 1
+  version: 1.30.1
+- repository:
+  - fedora/42
+  - fedora/43
+  - fedora/44
+  image: git.unkin.net/unkin/almalinux9-rpmbuilder:latest
+  release: 1
+  version: 1.30.1

rpms/kubectl-cnpg/resources/build.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/bash
+
+set -e
+
+BASE_URL="https://artifactapi.k8s.syd1.au.unkin.net/api/v1/remote/github/cloudnative-pg/cloudnative-pg/releases/download/v${PACKAGE_VERSION}"
+TARBALL="kubectl-cnpg_${PACKAGE_VERSION}_linux_x86_64.tar.gz"
+
+wget -O "/app/${TARBALL}" "${BASE_URL}/${TARBALL}"
+wget -O /app/checksums.txt "${BASE_URL}/cnpg-${PACKAGE_VERSION}-checksums.txt"
+
+cd /app
+grep " ${TARBALL}$" checksums.txt | sha256sum --check --strict -
+tar xf "/app/${TARBALL}" -C /app/ kubectl-cnpg
+
+mkdir -p /app/completions
+/app/kubectl-cnpg completion bash > /app/completions/kubectl-cnpg
+/app/kubectl-cnpg completion zsh > /app/completions/_kubectl-cnpg
+/app/kubectl-cnpg completion fish > /app/completions/kubectl-cnpg.fish
+
+envsubst < /app/resources/nfpm.yaml > /app/nfpm.yaml
+
+nfpm pkg --config /app/nfpm.yaml --target /app/dist --packager rpm

rpms/kubectl-cnpg/resources/kubectl_complete-cnpg

@@ -0,0 +1,2 @@
+#!/usr/bin/env sh
+exec kubectl cnpg __complete "$@"

rpms/kubectl-cnpg/resources/nfpm.yaml

@@ -0,0 +1,54 @@
+# nfpm.yaml
+
+name: ${PACKAGE_NAME}
+version: ${PACKAGE_VERSION}
+release: ${PACKAGE_RELEASE}
+arch: ${PACKAGE_ARCH}
+platform: ${PACKAGE_PLATFORM}
+section: default
+priority: extra
+description: "${PACKAGE_DESCRIPTION}"
+
+maintainer: ${PACKAGE_MAINTAINER}
+homepage: ${PACKAGE_HOMEPAGE}
+license: ${PACKAGE_LICENSE}
+
+disable_globbing: false
+
+replaces:
+  - kubectl-cnpg
+
+provides:
+  - kubectl-cnpg
+
+contents:
+  - src: /app/kubectl-cnpg
+    dst: /usr/bin/kubectl-cnpg
+    file_info:
+      mode: 0755
+      owner: root
+      group: root
+  - src: /app/resources/kubectl_complete-cnpg
+    dst: /usr/bin/kubectl_complete-cnpg
+    file_info:
+      mode: 0755
+      owner: root
+      group: root
+  - src: /app/completions/kubectl-cnpg
+    dst: /usr/share/bash-completion/completions/kubectl-cnpg
+    file_info:
+      mode: 0644
+      owner: root
+      group: root
+  - src: /app/completions/_kubectl-cnpg
+    dst: /usr/share/zsh/site-functions/_kubectl-cnpg
+    file_info:
+      mode: 0644
+      owner: root
+      group: root
+  - src: /app/completions/kubectl-cnpg.fish
+    dst: /usr/share/fish/vendor_completions.d/kubectl-cnpg.fish
+    file_info:
+      mode: 0644
+      owner: root
+      group: root