[mike@mwxm4]

main.go

@@ -45,6 +45,13 @@ var (
 )
 
 func main() {
+	// Answered before setup(), which exits when nothing is configured yet: an
+	// update has to work on a machine that has never run mgsh, and `--version`
+	// is what the freshly downloaded binary is probed with, right there.
+	if updateFlags() {
+		return
+	}
+
 	setup()
 	useColor = readline.IsTerminal(int(os.Stdout.Fd()))
 
@@ -68,12 +75,52 @@ func main() {
 		}
 		updateDirState()
 		runCommand(cmdline)
+		updateNote() // after the output: a footer, not a headline
 		return
 	}
 
+	updateNote() // before the prompt: a session starts here, not when it ends
 	runInteractive()
 }
 
+// updateFlags answers the self-update options and reports whether it did. They
+// are deliberately spelled with dashes and kept out of parseArgs: `mgsh update`
+// is the command for everyday use, and these are what works when there is no
+// configuration to read yet.
+func updateFlags() bool {
+	if len(os.Args) < 2 {
+		return false
+	}
+	switch os.Args[1] {
+	case "--version":
+		fmt.Printf("mgsh %s\n", VERSION)
+	case "--update":
+		if err := selfUpdate.install(os.Stdout); err != nil {
+			fmt.Fprintf(os.Stderr, "mgsh: %v\n", err)
+			os.Exit(1)
+		}
+	case "--check-update":
+		if err := selfUpdate.check(os.Stdout); err != nil {
+			fmt.Fprintf(os.Stderr, "mgsh: %v\n", err)
+			os.Exit(1)
+		}
+	case updateRefreshFlag: // the background run, not in the help
+		selfUpdate.refresh()
+	default:
+		return false
+	}
+	return true
+}
+
+// updateNote prints the once-a-day hint, when there is one. It costs nothing:
+// the line comes from the note in the cache directory, and the asking behind it
+// happens in the background, at most once a day.
+func updateNote() {
+	if hint := selfUpdate.daily(); hint != "" {
+		fmt.Fprintln(os.Stderr, col(cDark, hint))
+	}
+}
+
 // runInteractive drives the colored, history- and completion-enabled REPL.
 func runInteractive() {
 	home, _ := os.UserHomeDir()
@@ -148,6 +195,7 @@ func parseArgs() (int, string, bool) {
 		"push": 1, "pushremote": 1, "deleteremote": 1, "list": 1, "tag": 1, "archive": 1, "show": 1,
 		"pull": 1, "fetch": 1, "status": 1, "diff": 1, "overview": 1,
 		"config": 1, "count": 1, "login": 1, "cloneall": 1, "release": 1,
+		"update": 1,
 	}
 	if c, ok := cls[a0]; ok {
 		return c, strings.Join(os.Args[1:], " "), false