fix default value set for bool type (#273)

Author: AllyW

knack/commands.py

@@ -124,7 +124,10 @@ def update_argument(self, param_name, argtype):
         # that coincides with the default
         if isinstance(arg_default, str):
             arg_default = DefaultStr(arg_default)
-        elif isinstance(arg_default, int):
+        elif isinstance(arg_default, int) and not isinstance(arg_default, bool):
+            # bool's is_default is ignored for now, because
+            # 1. bool is a subclass of int, so isinstance(True, int) cannot distinguish between int and bool
+            # 2. bool is not extendable according to https://stackoverflow.com/a/2172204/2199657
             arg_default = DefaultInt(arg_default)
         # update the default
         if arg_default: