Add update command and auto-update check

Introduce an internal update checker and a new CLI command. Adds internal/update package that queries GitHub releases (lnbotdev/cli) with a 3s timeout and 24h cache interval, storing results at ~/.config/lnbot/.update-check and honoring LNBOT_NO_UPDATE_CHECK. Adds cmd/update.go (cobra command) to show current/latest versions and platform-specific upgrade instructions. Integrates the update check into root.PersistentPostRun to notify users when an update is available and registers the update command in the command groups.

Author: realbub

cmd/root.go

@@ -11,6 +11,7 @@ import (
 	lnbot "github.com/lnbotdev/go-sdk"
 
 	"github.com/lnbotdev/cli/internal/config"
+	"github.com/lnbotdev/cli/internal/update"
 )
 
 var (
@@ -39,6 +40,12 @@ var rootCmd = &cobra.Command{
 		cfg, err = config.Load()
 		return err
 	},
+	PersistentPostRun: func(cmd *cobra.Command, args []string) {
+		if latest, ok := update.CheckForUpdate(version); ok {
+			fmt.Fprintf(os.Stderr, "\nUpdate available: %s → %s\n", version, latest)
+			fmt.Fprintf(os.Stderr, "Run: curl -fsSL https://ln.bot/install.sh | bash\n")
+		}
+	},
 }
 
 const rootHelpTmpl = `{{.Long}}
@@ -133,6 +140,7 @@ func init() {
 	webhookCmd.GroupID = "integrations"
 	mcpCmd.GroupID = "integrations"
 
+	updateCmd.GroupID = "other"
 	completionCmd.GroupID = "other"
 	versionCmd.GroupID = "other"
 
@@ -151,6 +159,7 @@ func init() {
 	rootCmd.AddCommand(addressCmd)
 	rootCmd.AddCommand(webhookCmd)
 	rootCmd.AddCommand(mcpCmd)
+	rootCmd.AddCommand(updateCmd)
 	rootCmd.AddCommand(versionCmd)
 
 	cobra.AddTemplateFuncs(template.FuncMap{
@@ -174,7 +183,7 @@ func init() {
 	// Leaf commands: use default cobra template (don't inherit root's grouped template)
 	leafCmds := []*cobra.Command{
 		initCmd, balanceCmd, statusCmd, whoamiCmd, payCmd, transactionsCmd,
-		completionCmd, versionCmd,
+		updateCmd, completionCmd, versionCmd,
 	}
 	for _, cmd := range leafCmds {
 		cmd.SetHelpTemplate(leafHelpTmpl)

cmd/update.go

@@ -0,0 +1,38 @@
+package cmd
+
+import (
+	"fmt"
+	"runtime"
+
+	"github.com/spf13/cobra"
+
+	"github.com/lnbotdev/cli/internal/update"
+)
+
+var updateCmd = &cobra.Command{
+	Use:   "update",
+	Short: "Check for updates or show upgrade instructions",
+	Long:  `Check if a newer version of lnbot is available and show how to upgrade.`,
+	Example: `  lnbot update`,
+	Run: func(cmd *cobra.Command, args []string) {
+		fmt.Printf("Current version: %s\n", version)
+
+		latest, available := update.CheckForUpdate(version)
+		if !available {
+			fmt.Println("You're up to date.")
+			return
+		}
+
+		fmt.Printf("Latest version:  %s\n", latest)
+		fmt.Println()
+		fmt.Println("To update:")
+
+		switch runtime.GOOS {
+		case "windows":
+			fmt.Println("  PowerShell: iwr -useb https://ln.bot/install.ps1 | iex")
+			fmt.Println("  CMD:        curl -fsSL https://ln.bot/install.cmd -o install.cmd && install.cmd && del install.cmd")
+		default:
+			fmt.Println("  curl -fsSL https://ln.bot/install.sh | bash")
+		}
+	},
+}

internal/update/update.go

@@ -0,0 +1,97 @@
+package update
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const (
+	repo         = "lnbotdev/cli"
+	checkTimeout = 3 * time.Second
+	checkInterval = 24 * time.Hour
+)
+
+type cachedCheck struct {
+	Latest    string `json:"latest"`
+	CheckedAt int64  `json:"checked_at"`
+}
+
+func cacheFile() string {
+	home, _ := os.UserHomeDir()
+	return filepath.Join(home, ".config", "lnbot", ".update-check")
+}
+
+func CheckForUpdate(current string) (latest string, available bool) {
+	if os.Getenv("LNBOT_NO_UPDATE_CHECK") != "" {
+		return "", false
+	}
+
+	// Check cache first
+	if data, err := os.ReadFile(cacheFile()); err == nil {
+		var cached cachedCheck
+		if json.Unmarshal(data, &cached) == nil {
+			if time.Since(time.Unix(cached.CheckedAt, 0)) < checkInterval {
+				if cached.Latest != "" && cached.Latest != current {
+					return cached.Latest, true
+				}
+				return "", false
+			}
+		}
+	}
+
+	// Fetch latest release from GitHub
+	latest, err := fetchLatest()
+	if err != nil {
+		return "", false
+	}
+
+	// Cache the result
+	saveCache(latest)
+
+	if latest != current && latest != "" {
+		return latest, true
+	}
+	return "", false
+}
+
+func fetchLatest() (string, error) {
+	client := &http.Client{Timeout: checkTimeout}
+	url := fmt.Sprintf("https://api.github.com/repos/%s/releases/latest", repo)
+
+	resp, err := client.Get(url)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return "", fmt.Errorf("status %d", resp.StatusCode)
+	}
+
+	var release struct {
+		TagName string `json:"tag_name"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
+		return "", err
+	}
+
+	tag := release.TagName
+	if len(tag) > 0 && tag[0] == 'v' {
+		tag = tag[1:]
+	}
+	return tag, nil
+}
+
+func saveCache(latest string) {
+	data, _ := json.Marshal(cachedCheck{
+		Latest:    latest,
+		CheckedAt: time.Now().Unix(),
+	})
+	p := cacheFile()
+	os.MkdirAll(filepath.Dir(p), 0o700)
+	os.WriteFile(p, data, 0o600)
+}