Add the symbol option and its default.

src/cipher_analytical_machine/cli.clj

@@ -2,6 +2,7 @@
   (:require
    [cipher-analytical-machine.file :as file]
    [cipher-analytical-machine.caesar :as caesar]
+   [cipher-analytical-machine.symbol-factories :as sf]
    [clojure.string :as cs]
    [clojure.tools.cli :refer [parse-opts]])
   (:gen-class))
@@ -17,6 +18,8 @@
     :default "Caesar"]
    ["-e" "--encrypt" "Encrypt the message."]
    ["-d" "--decrypt" "Decrypt the message."]
+   ["-s" "--symbols" "The string will be used as a set of symbols for a cipher."
+    :default (sf/default-symbol-factory "en")]
    ["-h" "--help"]])
 
 (defn usage [options-summary]