preserve name, author, version, and logger in case cli.milc_options()…

… is called multiple times

docs/metadata.md

@@ -12,21 +12,19 @@ cli.milc_options(name='Florzelbop', version='1.0.0', author='Jane Doe')
 
 You should only do this once, and you should do it as early in your program's execution as possible.
 
-!!! danger
-    Do not import `set_metadata` and `cli` at the same time! When you run `set_metadata` the `cli` object will be replaced, but your existing import will continue to reference the old `cli` object.
+!!! warning
+    If you have spread your program among several files, or you are using `milc.subcommand.config`, you need to use `cli.milc_options()` before you import those modules.
 
 ## Custom Loggers
 
 You can also use this to pass in custom loggers.
 
 ```python
-from milc import set_metadata
+from milc import cli
 
 from my_program import custom_logger
 
-set_metadata(logger=custom_logger)
-
-from milc import cli
+cli.milc_options(logger=custom_logger)
 ```
 
 ## Deprecated: set_metadata()

milc/milc_interface.py

@@ -18,12 +18,20 @@
 class MILCInterface:
     def __init__(self) -> None:
         self._milc: Optional[MILC] = None
+        self._name = None
+        self._author = None
+        self._version = None
+        self._logger = None
 
     def milc_options(self, *, name: Optional[str] = None, author: Optional[str] = None, version: Optional[str] = None, logger: Optional[Logger] = None) -> None:
         if self._milc and self._milc._inside_context_manager:
             raise RuntimeError('You must run set_metadata() before cli()!')
 
-        self._milc = MILC(name, author, version, logger)
+        self._name = name or self._name
+        self._author = author or self._author
+        self._version = version or self._version
+        self._logger = logger or self._logger
+        self._milc = MILC(self._name, self._author, self._version, self._logger)
 
     @property
     def milc(self) -> MILC: