From 9f0793ab0f7f73f8829cb86d6a645fd01eaa6849 Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher <jakobunt@gmail.com>
Date: Sun, 9 Oct 2016 20:55:33 +0200
Subject: [PATCH] main: more useful error message on unknown flag

---
 cli_args.go | 18 ++++++++++++++++--
 main.go     |  4 +---
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/cli_args.go b/cli_args.go
index 2d5ad7e..9ba5496 100644
--- a/cli_args.go
+++ b/cli_args.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"os"
 	"strconv"
 	"strings"
@@ -57,7 +58,7 @@ func parseCliOpts() (args argContainer) {
 	var err error
 	var opensslAuto string
 
-	flagSet = flag.NewFlagSet(tlog.ProgramName, flag.ExitOnError)
+	flagSet = flag.NewFlagSet(tlog.ProgramName, flag.ContinueOnError)
 	flagSet.Usage = usageText
 	flagSet.BoolVar(&args.debug, "d", false, "")
 	flagSet.BoolVar(&args.debug, "debug", false, "Enable debug output")
@@ -99,7 +100,12 @@ func parseCliOpts() (args argContainer) {
 	flagSet.BoolVar(&ignoredBool, "nosuid", false, ignoreText)
 	flagSet.BoolVar(&ignoredBool, "nodev", false, ignoreText)
 	// Actual parsing
-	flagSet.Parse(os.Args[1:])
+	err = flagSet.Parse(os.Args[1:])
+	if err != nil {
+		tlog.Warn.Printf("You passed: %s", prettyArgs())
+		tlog.Fatal.Printf("%v", err)
+		os.Exit(2)
+	}
 
 	// "-openssl" needs some post-processing
 	if opensslAuto == "auto" {
@@ -117,3 +123,11 @@ func parseCliOpts() (args argContainer) {
 	}
 	return args
 }
+
+// prettyArgs pretty-prints the command-line arguments.
+func prettyArgs() string {
+	pa := fmt.Sprintf("%q", os.Args[1:])
+	// Get rid of "[" and "]"
+	pa = pa[1 : len(pa)-1]
+	return pa
+}
diff --git a/main.go b/main.go
index 6d03ee2..c5675e2 100644
--- a/main.go
+++ b/main.go
@@ -216,9 +216,7 @@ func main() {
 	}
 	// Default operation: mount.
 	if flagSet.NArg() != 2 {
-		prettyArgs := fmt.Sprintf("%q", os.Args[1:])
-		// Get rid of "[" and "]"
-		prettyArgs = prettyArgs[1 : len(prettyArgs)-1]
+		prettyArgs := prettyArgs()
 		tlog.Info.Printf("Wrong number of arguments (have %d, want 2). You passed: %s",
 			flagSet.NArg(), prettyArgs)
 		tlog.Fatal.Printf("Usage: %s [OPTIONS] CIPHERDIR MOUNTPOINT [-o COMMA-SEPARATED-OPTIONS]", tlog.ProgramName)