Stubs out pm key create subcommand

cmd/pm/main.go

@@ -11,20 +11,37 @@ subcommands:
   keyring    (key) -- interact with pm's OpenPGP keyring
 `
 
+const keyUsage = `pm keyring: interact with pm's OpenPGP keyring
+
+subcommands:
+  create      (c)  --  create a fresh keypair
+`
+
 func main() {
 	if len(os.Args) < 2 {
-		fatal(usage)
+		fatalf("pm: missing subcommand\n\n%v", usage)
 	}
 	cmd := os.Args[1]
 
 	switch cmd {
 	case "key", "keyring":
+		if len(os.Args[1:]) < 2 {
+			fatalf("pm keyring: insufficient args\n\nusage: %v", keyUsage)
+		}
+		sub := os.Args[2]
+		switch sub {
+		case "c", "create":
+			fmt.Printf("creating keyring ...\n")
+			fatalf("NYI\n")
 		default:
-		fatal("uknown subcommand %q\n\nusage: %v", cmd, usage)
+			fatalf("unknown keyring subcommand: %q\n\nusage: %v", sub, keyUsage)
+		}
+	default:
+		fatalf("uknown subcommand %q\n\nusage: %v", cmd, usage)
 	}
 }
 
-func fatal(f string, args ...interface{}) {
+func fatalf(f string, args ...interface{}) {
 	fmt.Fprintf(os.Stderr, f, args...)
 	os.Exit(1)
 }