feat: start publishing release metadata json file (#199)

whenever a release is built we now publish a metadata json file with a
content similar to this:

```json
{
        "Versions": {
                "AdminConsole": "v1.104.3",
                "EmbeddedClusterOperator": "v0.4.1",
                "Installer": "v1.28.4+ec.0-dirty",
                "Kubernetes": "v1.28.4+k0s.0",
                "OpenEBS": "v3.9.0"
        },
        "K0sSHA": "926bcb68478f0eb5bb8479bf01d39524102346d9f24b9f536aeddf71fdd5a975"
}
```

a new hidden topic has been added to the version topic, this is how we
generate the version (or release) metadata:

```
$ embedded-cluster version metadata
{
        "Versions": {
                "AdminConsole": "v1.104.3",
                "EmbeddedClusterOperator": "v0.4.1",
                "Installer": "v1.28.4+ec.0-dirty",
                "Kubernetes": "v1.28.4+k0s.0",
                "OpenEBS": "v3.9.0"
        },
        "K0sSHA": "926bcb68478f0eb5bb8479bf01d39524102346d9f24b9f536aeddf71fdd5a975"
}
$
```

.github/workflows/release-dev.yaml

@@ -21,6 +21,7 @@ jobs:
         run: |
           make embedded-cluster-linux-amd64
           tar -C output/bin -czvf embedded-cluster-linux-amd64.tgz embedded-cluster
+          ./output/bin/embedded-cluster version metadata > metadata.json
           make clean
       - name: Build darwin-amd64
         run: |
@@ -41,3 +42,4 @@ jobs:
           title: Development Release Build
           files: |
             *.tgz
+            metadata.json

.github/workflows/release-prod.yaml

@@ -23,6 +23,7 @@ jobs:
         run: |
           make embedded-cluster-linux-amd64 VERSION=$TAG_NAME
           tar -C output/bin -czvf embedded-cluster-linux-amd64.tgz embedded-cluster
+          ./output/bin/embedded-cluster version metadata > metadata.json
           make clean
       - name: Build darwin-amd64
         run: |
@@ -41,3 +42,4 @@ jobs:
           prerelease: false
           files: |
             *.tgz
+            metadata.json

cmd/embedded-cluster/version.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"fmt"
 	"strings"
 
@@ -9,11 +10,13 @@ import (
 
 	"github.com/replicatedhq/embedded-cluster/pkg/addons"
 	"github.com/replicatedhq/embedded-cluster/pkg/defaults"
+	"github.com/replicatedhq/embedded-cluster/pkg/goods"
 )
 
 var versionCommand = &cli.Command{
-	Name:  "version",
-	Usage: fmt.Sprintf("Shows the %s installer version", defaults.BinaryName()),
+	Name:        "version",
+	Usage:       fmt.Sprintf("Shows the %s installer version", defaults.BinaryName()),
+	Subcommands: []*cli.Command{metadataCommand},
 	Action: func(c *cli.Context) error {
 		opts := []addons.Option{addons.Quiet(), addons.WithoutPrompt()}
 		versions, err := addons.NewApplier(opts...).Versions()
@@ -34,3 +37,36 @@ var versionCommand = &cli.Command{
 		return nil
 	},
 }
+
+// ReleaseMetadata holds the metadata about a specific release, including addons and
+// their versions.
+type ReleaseMetadata struct {
+	Versions map[string]string
+	K0sSHA   string
+}
+
+var metadataCommand = &cli.Command{
+	Name:   "metadata",
+	Usage:  "Print metadata about this release",
+	Hidden: true,
+	Action: func(c *cli.Context) error {
+		opts := []addons.Option{addons.Quiet(), addons.WithoutPrompt()}
+		versions, err := addons.NewApplier(opts...).Versions()
+		if err != nil {
+			return fmt.Errorf("unable to get versions: %w", err)
+		}
+		versions["Kubernetes"] = defaults.K0sVersion
+		versions["Installer"] = defaults.Version
+		sha, err := goods.K0sBinarySHA256()
+		if err != nil {
+			return fmt.Errorf("unable to get k0s binary sha256: %w", err)
+		}
+		meta := ReleaseMetadata{Versions: versions, K0sSHA: sha}
+		data, err := json.MarshalIndent(meta, "", "\t")
+		if err != nil {
+			return fmt.Errorf("unable to marshal versions: %w", err)
+		}
+		fmt.Println(string(data))
+		return nil
+	},
+}

pkg/goods/goods.go

@@ -3,9 +3,13 @@
 package goods
 
 import (
+	"crypto/sha256"
 	"embed"
+	"encoding/hex"
 	"fmt"
+	"io"
 	"os"
+	"path"
 	"runtime"
 	"strings"
 
@@ -15,6 +19,22 @@ import (
 //go:embed bins/*
 var binfs embed.FS
 
+// K0sBinarySHA256 returns the SHA256 checksum of the embedded k0s binary.
+func K0sBinarySHA256() (string, error) {
+	fname := fmt.Sprintf("k0s-%s", defaults.K0sVersion)
+	binpath := path.Join("bins", "k0sctl", fname)
+	fp, err := binfs.Open(binpath)
+	if err != nil {
+		return "", fmt.Errorf("unable to open embedded k0s binary: %w", err)
+	}
+	defer fp.Close()
+	hasher := sha256.New()
+	if _, err := io.Copy(hasher, fp); err != nil {
+		return "", fmt.Errorf("unable to copy embedded k0s binary: %w", err)
+	}
+	return hex.EncodeToString(hasher.Sum(nil)), nil
+}
+
 // Materialize writes to disk embed assets.
 func Materialize() error {
 	entries, err := binfs.ReadDir("bins/k0sctl")