cmd/tailscale/cli: make set's usage match up's, other than defaults

Fixes #6082

Change-Id: I92dc4726d866dcfd87e93ff09772601851d92ccf
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/cli.go

@@ -297,55 +297,14 @@ func strSliceContains(ss []string, s string) bool {
 
 // usageFuncNoDefaultValues is like usageFunc but doesn't print default values.
 func usageFuncNoDefaultValues(c *ffcli.Command) string {
-	var b strings.Builder
-
-	fmt.Fprintf(&b, "USAGE\n")
-	if c.ShortUsage != "" {
-		fmt.Fprintf(&b, "  %s\n", c.ShortUsage)
-	} else {
-		fmt.Fprintf(&b, "  %s\n", c.Name)
-	}
-	fmt.Fprintf(&b, "\n")
-
-	if c.LongHelp != "" {
-		fmt.Fprintf(&b, "%s\n\n", c.LongHelp)
-	}
-
-	if len(c.Subcommands) > 0 {
-		fmt.Fprintf(&b, "SUBCOMMANDS\n")
-		tw := tabwriter.NewWriter(&b, 0, 2, 2, ' ', 0)
-		for _, subcommand := range c.Subcommands {
-			fmt.Fprintf(tw, "  %s\t%s\n", subcommand.Name, subcommand.ShortHelp)
-		}
-		tw.Flush()
-		fmt.Fprintf(&b, "\n")
-	}
-
-	if countFlags(c.FlagSet) > 0 {
-		fmt.Fprintf(&b, "FLAGS\n")
-		tw := tabwriter.NewWriter(&b, 0, 2, 2, ' ', 0)
-		c.FlagSet.VisitAll(func(f *flag.Flag) {
-			var s string
-			name, usage := flag.UnquoteUsage(f)
-			s = fmt.Sprintf("  --%s", f.Name) // Two spaces before --; see next two comments.
-			if len(name) > 0 {
-				s += " " + name
-			}
-			// Four spaces before the tab triggers good alignment
-			// for both 4- and 8-space tab stops.
-			s += "\n    \t"
-			s += strings.ReplaceAll(usage, "\n", "\n    \t")
-
-			fmt.Fprintln(&b, s)
-		})
-		tw.Flush()
-		fmt.Fprintf(&b, "\n")
-	}
-
-	return strings.TrimSpace(b.String())
+	return usageFuncOpt(c, false)
 }
 
 func usageFunc(c *ffcli.Command) string {
+	return usageFuncOpt(c, true)
+}
+
+func usageFuncOpt(c *ffcli.Command, withDefaults bool) string {
 	var b strings.Builder
 
 	fmt.Fprintf(&b, "USAGE\n")
@@ -389,7 +348,7 @@ func usageFunc(c *ffcli.Command) string {
 			s += "\n    \t"
 			s += strings.ReplaceAll(usage, "\n", "\n    \t")
 
-			if f.DefValue != "" {
+			if f.DefValue != "" && withDefaults {
 				s += fmt.Sprintf(" (default %s)", f.DefValue)
 			}