docs: add Kubernetes version support list (#2661)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

CODEOWNERS

@@ -30,6 +30,7 @@
 /hack/remove-tf-providers @katexochen
 /hack/terraform @3u13r
 /hack/tools @katexochen
+/hack/versioninfogen @daniel-weisse
 /image @malt3
 /internal/api @derpsteb
 /internal/atls @thomasten

bazel/ci/BUILD.bazel

@@ -454,6 +454,17 @@ sh_template(
     template = "terraform_docgen.sh.in",
 )
 
+sh_template(
+    name = "version_info_gen",
+    data = [
+        "//hack/versioninfogen",
+    ],
+    substitutions = {
+        "@@VERSIONINFOGEN@@": "$(rootpath //hack/versioninfogen:versioninfogen)",
+    },
+    template = "version_info_gen.sh.in",
+)
+
 alias(
     name = "com_github_katexochen_ghh",
     actual = select({
@@ -553,6 +564,7 @@ multirun(
         ":proto_generate",
         ":cli_docgen",
         ":terraform_docgen",
+        ":version_info_gen",
     ],
     jobs = 0,  # execute concurrently
     visibility = ["//visibility:public"],

bazel/ci/version_info_gen.sh.in

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+###### script header ######
+
+lib=$(realpath @@BASE_LIB@@) || exit 1
+stat "${lib}" >> /dev/null || exit 1
+
+# shellcheck source=../sh/lib.bash
+if ! source "${lib}"; then
+  echo "Error: could not find import"
+  exit 1
+fi
+
+versioninfogen=$(realpath @@VERSIONINFOGEN@@)
+stat "${versioninfogen}" >> /dev/null
+
+cd "${BUILD_WORKSPACE_DIRECTORY}"
+
+###### script body ######
+
+cd hack/versioninfogen
+${versioninfogen}

docs/docs/architecture/versions.md

@@ -12,3 +12,10 @@ New releases are published on [GitHub](https://github.com/edgelesssys/constellat
 Constellation is aligned to the [version support policy of Kubernetes](https://kubernetes.io/releases/version-skew-policy/#supported-versions), and therefore usually supports the most recent three minor versions.
 When a new minor version of Kubernetes is released, support is added to the next Constellation release, and that version then supports four Kubernetes versions.
 Subsequent Constellation releases drop support for the oldest (and deprecated) Kubernetes version.
+
+The following Kubernetes versions are currently supported:
+<!--AUTO_GENERATED_BY_BAZEL-->
+<!--DO_NOT_EDIT-->
+* v1.26.10
+* v1.27.7
+* v1.28.3

hack/versioninfogen/BUILD.bazel

@@ -0,0 +1,18 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
+
+go_library(
+    name = "versioninfogen_lib",
+    srcs = ["main.go"],
+    importpath = "github.com/edgelesssys/constellation/v2/hack/versioninfogen",
+    visibility = ["//visibility:private"],
+    deps = [
+        "//internal/semver",
+        "//internal/versions",
+    ],
+)
+
+go_binary(
+    name = "versioninfogen",
+    embed = [":versioninfogen_lib"],
+    visibility = ["//visibility:public"],
+)

hack/versioninfogen/main.go

@@ -0,0 +1,74 @@
+/*
+Copyright (c) Edgeless Systems GmbH
+
+SPDX-License-Identifier: AGPL-3.0-only
+*/
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/edgelesssys/constellation/v2/internal/semver"
+	"github.com/edgelesssys/constellation/v2/internal/versions"
+)
+
+const fileSeparator = "<!--AUTO_GENERATED_BY_BAZEL-->\n<!--DO_NOT_EDIT-->\n"
+
+func main() {
+	filePath := flag.String("file-path", "../../docs/docs/architecture/versions.md", "path to the version file to update")
+	flag.Parse()
+
+	k8sVersionStrings := versions.SupportedK8sVersions()
+	var k8sVersions []semver.Semver
+	for _, k8sVersionString := range k8sVersionStrings {
+		k8sVersion, err := semver.New(k8sVersionString)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "invalid kubernetes version %q: %s", k8sVersionString, err)
+			os.Exit(1)
+		}
+		k8sVersions = append(k8sVersions, k8sVersion)
+	}
+
+	if err := updateDocFile(*filePath, k8sVersions); err != nil {
+		fmt.Fprintf(os.Stderr, "error updating versions file: %s\n", err)
+		os.Exit(1)
+	}
+}
+
+func updateDocFile(filePath string, supportedVersions []semver.Semver) error {
+	fileHeader, err := readVersionsFile(filePath)
+	if err != nil {
+		return err
+	}
+
+	var versionList strings.Builder
+	for _, version := range supportedVersions {
+		if _, err := versionList.WriteString(
+			fmt.Sprintf("* %s\n", version.String()),
+		); err != nil {
+			return fmt.Errorf("writing matrix doc file: %w", err)
+		}
+	}
+
+	return os.WriteFile(filePath, []byte(fileHeader+fileSeparator+versionList.String()), 0o644)
+}
+
+func readVersionsFile(filePath string) (string, error) {
+	f, err := os.Open(filePath)
+	if err != nil {
+		return "", fmt.Errorf("opening version info file: %w", err)
+	}
+	defer f.Close()
+
+	fileContentRaw, err := io.ReadAll(f)
+	if err != nil {
+		return "", fmt.Errorf("reading version info file: %w", err)
+	}
+	fileContent := strings.Split(string(fileContentRaw), fileSeparator)
+	return fileContent[0], nil
+}