Document "--" to stop option parsing in help text + man page

Documentation/MANPAGE.md

@@ -201,6 +201,10 @@ Options:
 :	Use all-zero dummy master key. This options is only intended for
 	automated testing as it does not provide any security.
 
+**--**
+:	Stop option parsing. Helpful when CIPHERDIR may start with a
+	dash "-".
+
 EXAMPLES
 ========
 

main.go

@@ -48,6 +48,9 @@ Options:
 `, tlog.ProgramName, tlog.ProgramName)
 
 	flagSet.PrintDefaults()
+	fmt.Print(`  --
+    	Stop option parsing
+`)
 }
 
 // loadConfig loads the config file "args.config", prompting the user for the password