main: rename "-o" option to "-ko"

This prevents confusion with the "-o" options that is passed
by mount(1) at the end of the command line.

Documentation/MANPAGE.md

@@ -65,6 +65,15 @@ to mount the gocryptfs filesytem without user interaction.
 **-init**
 :	Initialize encrypted directory
 
+**-ko**
+: Pass additonal mount options to the kernel (comma-separated list).
+FUSE filesystems are mounted with "nodev,nosuid" by default. If gocryptfs
+runs as root, you can enable device files by passing the opposite mount option,
+"dev", and if you want to enable suid-binaries, pass "suid".
+"ro" (equivalent to passing the "-ro" option) and "noexec" may also be
+interesting. For a complete list see the section
+`FILESYSTEM-INDEPENDENT MOUNT OPTIONS` in mount(8).
+
 **-longnames**
 :	Store names longer than 176 bytes in extra files (default true)
 This flag is useful when recovering old gocryptfs filesystems using
@@ -93,15 +102,6 @@ continue be printed to stdout and stderr.
 :	Send USR1 to the specified process after successful mount. This is
 used internally for daemonization.
 
-**-o**
-: Pass additonal mount options to the kernel (comma-separated list).
-FUSE filesystems are mounted with "nodev,nosuid" by default. If gocryptfs
-runs as root, you can enable device files by passing the opposite mount option,
-"dev", and if you want to enable suid-binaries, pass "suid".
-"ro" (equivalent to passing the "-ro" option) and "noexec" may also be
-interesting. For a complete list see the section
-`FILESYSTEM-INDEPENDENT MOUNT OPTIONS` in mount(8).
-
 **-openssl bool/"auto"**
 :	Use OpenSSL instead of built-in Go crypto (default "auto"). Using
 built-in crypto is 4x slower unless your CPU has AES instructions and

cli_args.go

@@ -16,7 +16,7 @@ type argContainer struct {
 	plaintextnames, quiet, nosyslog, wpanic,
 	longnames, allow_other, ro, reverse, aessiv, nonempty bool
 	masterkey, mountpoint, cipherdir, cpuprofile, extpass,
-	memprofile, o string
+	memprofile, ko string
 	// Configuration file name override
 	config             string
 	notifypid, scryptn int
@@ -61,7 +61,7 @@ func parseCliOpts() (args argContainer) {
 	flagSet.StringVar(&args.memprofile, "memprofile", "", "Write memory profile to specified file")
 	flagSet.StringVar(&args.config, "config", "", "Use specified config file instead of CIPHERDIR/gocryptfs.conf")
 	flagSet.StringVar(&args.extpass, "extpass", "", "Use external program for the password prompt")
-	flagSet.StringVar(&args.o, "o", "", "Pass additional mount options to the kernel, comma-separated list")
+	flagSet.StringVar(&args.ko, "ko", "", "Pass additional options directly to the kernel, comma-separated list")
 	flagSet.IntVar(&args.notifypid, "notifypid", 0, "Send USR1 to the specified process after "+
 		"successful mount - used internally for daemonization")
 	flagSet.IntVar(&args.scryptn, "scryptn", configfile.ScryptDefaultLogN, "scrypt cost parameter logN. "+

mount.go

@@ -185,9 +185,9 @@ func initFuseFrontend(key []byte, args *argContainer, confFile *configfile.ConfF
 	}
 	// Add additional mount options (if any) after the stock ones, so the user has
 	// a chance to override them.
-	if args.o != "" {
+	if args.ko != "" {
-		parts := strings.Split(args.o, ",")
+		parts := strings.Split(args.ko, ",")
-		tlog.Debug.Printf("Adding -o mount options: %v", parts)
+		tlog.Debug.Printf("Adding -ko mount options: %v", parts)
 		mOpts.Options = append(mOpts.Options, parts...)
 	}
 	srv, err := fuse.NewServer(conn.RawFS(), args.mountpoint, &mOpts)