add @classproperty, change set_repo to not require the parent

my/core/common.py

@@ -195,3 +195,27 @@ def fastermime(path: PathIsh) -> str:
 
 
 Json = Dict[str, Any]
+
+
+from typing import TypeVar, Callable, Generic
+
+_C = TypeVar('_C')
+_R = TypeVar('_R')
+
+# https://stackoverflow.com/a/5192374/706389
+class classproperty(Generic[_R]):
+    def __init__(self, f: Callable[[_C], _R]) -> None:
+        self.f = f
+
+    def __get__(self, obj: None, cls: _C) -> _R:
+        return self.f(cls)
+
+
+# hmm, this doesn't really work with mypy well..
+# https://github.com/python/mypy/issues/6244
+# class staticproperty(Generic[_R]):
+#     def __init__(self, f: Callable[[], _R]) -> None:
+#         self.f = f
+#
+#     def __get__(self) -> _R:
+#         return self.f()