CLI ignore prefix if validation_alias is set.

See pydantic#25

pydantic_settings/sources.py

@@ -1606,7 +1606,13 @@ def _add_parser_args(
                     )
                 elif is_alias_path_only:
                     continue
-                elif group is not None:
+
+                if arg_prefix and field_info.validation_alias is not None:
+                    # Strip prefix if validation alias is set and value is not complex.
+                    # See https://github.com/pydantic/pydantic-settings/pull/25
+                    kwargs['dest'] = kwargs['dest'][self.env_prefix_len:]
+
+                if group is not None:
                     if isinstance(group, dict):
                         group = self._add_argument_group(parser, **group)
                     added_args += list(arg_names)