fix(publisher): add --help support for subcommands (#867)

## Summary
- Added `printCommandHelp()` function to display help for each
subcommand
- `mcp-publisher init --help` now shows init command help instead of
running init
- `mcp-publisher login --help` now shows login methods instead of error
- `mcp-publisher publish --help` now shows publish usage instead of
attempting publish

Fixes #735

Signed-off-by: majiayu000 <1835304752@qq.com>
Co-authored-by: Radoslav Dimitrov <radoslav@stacklok.com>

cmd/publisher/main.go

@@ -27,6 +27,12 @@ func main() {
 		os.Exit(1)
 	}
 
+	// Check for help flag for subcommands
+	if len(os.Args) >= 3 && (os.Args[2] == "--help" || os.Args[2] == "-h") {
+		printCommandHelp(os.Args[1])
+		return
+	}
+
 	var err error
 	switch os.Args[1] {
 	case "init":
@@ -68,3 +74,59 @@ func printUsage() {
 	_, _ = fmt.Fprintln(os.Stdout)
 	_, _ = fmt.Fprintln(os.Stdout, "Use 'mcp-publisher <command> --help' for more information about a command.")
 }
+
+func printCommandHelp(command string) {
+	switch command {
+	case "init":
+		_, _ = fmt.Fprintln(os.Stdout, "Create a server.json file template")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Usage:")
+		_, _ = fmt.Fprintln(os.Stdout, "  mcp-publisher init")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "This command creates a server.json file in the current directory with")
+		_, _ = fmt.Fprintln(os.Stdout, "auto-detected values from your project (package.json, git remote, etc.).")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "After running init, edit the generated server.json to customize your")
+		_, _ = fmt.Fprintln(os.Stdout, "server's metadata before publishing.")
+
+	case "login":
+		_, _ = fmt.Fprintln(os.Stdout, "Authenticate with the registry")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Usage:")
+		_, _ = fmt.Fprintln(os.Stdout, "  mcp-publisher login <method> [options]")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Methods:")
+		_, _ = fmt.Fprintln(os.Stdout, "  github        Interactive GitHub authentication")
+		_, _ = fmt.Fprintln(os.Stdout, "  github-oidc   GitHub Actions OIDC authentication")
+		_, _ = fmt.Fprintln(os.Stdout, "  dns           DNS-based authentication (requires --domain)")
+		_, _ = fmt.Fprintln(os.Stdout, "  http          HTTP-based authentication (requires --domain)")
+		_, _ = fmt.Fprintln(os.Stdout, "  none          Anonymous authentication (for testing)")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Examples:")
+		_, _ = fmt.Fprintln(os.Stdout, "  mcp-publisher login github")
+		_, _ = fmt.Fprintln(os.Stdout, "  mcp-publisher login dns --domain example.com --private-key <key>")
+
+	case "logout":
+		_, _ = fmt.Fprintln(os.Stdout, "Clear saved authentication")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Usage:")
+		_, _ = fmt.Fprintln(os.Stdout, "  mcp-publisher logout")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "This command removes the saved authentication token from your system.")
+
+	case "publish":
+		_, _ = fmt.Fprintln(os.Stdout, "Publish server.json to the registry")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Usage:")
+		_, _ = fmt.Fprintln(os.Stdout, "  mcp-publisher publish [server.json]")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "Arguments:")
+		_, _ = fmt.Fprintln(os.Stdout, "  server.json   Path to the server.json file (default: ./server.json)")
+		_, _ = fmt.Fprintln(os.Stdout)
+		_, _ = fmt.Fprintln(os.Stdout, "You must be logged in before publishing. Run 'mcp-publisher login' first.")
+
+	default:
+		fmt.Fprintf(os.Stderr, "Unknown command: %s\n", command)
+		printUsage()
+	}
+}