Added show_default field

spec/help_spec.lua

@@ -116,6 +116,44 @@ Sets verbosity level.
       }, "\r\n"), parser:get_help())
    end)
 
+   it("shows default values", function()
+      local parser = Parser "foo"
+      parser:option "-o"
+         :default "a.out"
+      parser:option "-p"
+         :default "8080"
+         :description "Port."
+
+      assert.equal(table.concat({
+         "Usage: foo [-o <o>] [-p <p>] [-h]",
+         "",
+         "Options: ",
+         "   -o <o>                default: a.out",
+         "   -p <p>                Port. (default: 8080)",
+         "   -h, --help            Show this help message and exit. "
+      }, "\r\n"), parser:get_help())
+   end)
+
+   it("does not show default value when show_default == false", function()
+      local parser = Parser "foo"
+      parser:option "-o"
+         :default "a.out"
+         :show_default(false)
+      parser:option "-p"
+         :default "8080"
+         :show_default(false)
+         :description "Port. "
+
+      assert.equal(table.concat({
+         "Usage: foo [-o <o>] [-p <p>] [-h]",
+         "",
+         "Options: ",
+         "   -o <o>",
+         "   -p <p>                Port. ",
+         "   -h, --help            Show this help message and exit. "
+      }, "\r\n"), parser:get_help())
+   end)
+
    it("creates correct help message for commands", function()
       local parser = Parser "foo"
       parser:flag "-q" "--quiet"

src/argparse.lua

@@ -191,7 +191,8 @@ do -- Create classes with setters
       _maxargs = 1,
       _mincount = 1,
       _maxcount = 1,
-      _defmode = "unused"
+      _defmode = "unused",
+      _show_default = true
    }, {
       name = typecheck.string "name",
       description = typecheck.string "description",
@@ -200,7 +201,8 @@ do -- Create classes with setters
       default = typecheck.string "default",
       defmode = typecheck.string "defmode",
       convert = convert,
-      argname = argname
+      argname = argname,
+      show_default = typecheck.boolean "show_default"
    })
 
    Option = add_setters(Argument:extends {
@@ -220,7 +222,8 @@ do -- Create classes with setters
       convert = convert,
       overwrite = typecheck.boolean "overwrite",
       action = typecheck["function"] "action",
-      argname = argname
+      argname = argname,
+      show_default = typecheck.boolean "show_default"
    })
 end
 
@@ -329,7 +332,7 @@ function Command:_get_label()
 end
 
 function Argument:_get_description()
-   if self._default then
+   if self._default and self._show_default then
       if self._description then
          return ("%s (default: %s)"):format(self._description, self._default)
       else