core: proprely resolve class properties in make_config + add test

my/cfg.py

@@ -11,23 +11,9 @@ After that, you can set config attributes:
       export_path = '/path/to/twitter/exports'
   config.twitter = user_config
 """
+# TODO do I really need it?
+
 # todo why do we bring this into scope? don't remember..
 import my.config as config
 
-
-from pathlib import Path
-from typing import Union
-def set_repo(name: str, repo: Union[Path, str]) -> None:
-    from .core.init import assign_module
-    from . common import import_from
-
-    r = Path(repo)
-    module = import_from(r.parent, name)
-    assign_module('my.config.repos', name, module)
-
-
-# TODO set_repo is still useful, but perhaps move this thing away to core?
-
-# TODO ok, I need to get rid of this, better to rely on regular imports
-
 from .core import __NOT_HPI_MODULE__