main: also accept options at the end via "-o"

For compatability with mount(1), options are also accepted as
"-o COMMA-SEPARATED-OPTIONS" at the end of the command line.
For example, "-o q,zerokey" is equivalent to "-q -zerokey".

Documentation/MANPAGE.md

@@ -18,7 +18,7 @@ gocryptfs -init [OPTIONS] CIPHERDIR
 Mount
 -----
 
-gocryptfs [OPTIONS] CIPHERDIR MOUNTPOINT
+gocryptfs [OPTIONS] CIPHERDIR MOUNTPOINT [-o COMMA-SEPARATED-OPTIONS]
 
 Change password
 ---------------
@@ -143,6 +143,12 @@ useful in regression testing.
 automated testing as it does not provide any security.
 
 
+Comma-Separated-Options:
+
+For compatability with mount(1), options are also accepted as
+"-o COMMA-SEPARATED-OPTIONS" at the end of the command line.
+For example, "-o q,zerokey" is equivalent to "-q -zerokey".
+
 EXAMPLES
 ========
 

cli_args.go

@@ -4,6 +4,7 @@ import (
 	"flag"
 	"os"
 	"strconv"
+	"strings"
 
 	"github.com/rfjakob/gocryptfs/internal/configfile"
 	"github.com/rfjakob/gocryptfs/internal/prefer_openssl"
@@ -27,8 +28,32 @@ type argContainer struct {
 
 var flagSet *flag.FlagSet
 
+// prefixOArgs transform options passed via "-o foo,bar" into regular options
+// like "-foo -bar" and prefixes them to the command line.
+func prefixOArgs(osArgs []string) []string {
+	l := len(osArgs)
+	// Need at least 3, example: gocryptfs -o foo,bar
+	if l < 3 {
+		return osArgs
+	}
+	if osArgs[l-2] != "-o" {
+		return osArgs
+	}
+	oOpts := strings.Split(osArgs[l-1], ",")
+	osArgs = osArgs[:l-2]
+	newArgs := []string{osArgs[0]}
+	// Add options from "-o"
+	for _, a := range oOpts {
+		newArgs = append(newArgs, "-"+a)
+	}
+	newArgs = append(newArgs, osArgs[1:]...)
+	return newArgs
+}
+
 // parseCliOpts - parse command line options (i.e. arguments that start with "-")
 func parseCliOpts() (args argContainer) {
+	os.Args = prefixOArgs(os.Args)
+
 	var err error
 	var opensslAuto string
 

main.go

@@ -42,7 +42,7 @@ func usageText() {
 	printVersion()
 	fmt.Printf(`
 Usage: %s -init|-passwd [OPTIONS] CIPHERDIR
-  or   %s [OPTIONS] CIPHERDIR MOUNTPOINT
+  or   %s [OPTIONS] CIPHERDIR MOUNTPOINT [-o COMMA-SEPARATED-OPTIONS]
 
 Options:
 `, tlog.ProgramName, tlog.ProgramName)
@@ -221,7 +221,7 @@ func main() {
 		prettyArgs = prettyArgs[1 : len(prettyArgs)-1]
 		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", tlog.ProgramName)
+		tlog.Fatal.Printf("Usage: %s [OPTIONS] CIPHERDIR MOUNTPOINT [-o COMMA-SEPARATED-OPTIONS]", tlog.ProgramName)
 		os.Exit(ErrExitUsage)
 	}
 	os.Exit(doMount(&args))