Adding multiple configs (#685)

* Adding multiple configs

* Add type hinting

src/levanter/config.py

@@ -93,26 +93,51 @@ def _maybe_get_config_path_and_cmdline_args(args: List[str]):
     If URL, we need to download it and save it to a temp file. We then want to remove --config_path
     from the cmdline args so that draccus doesn't try to load it as a config path and return it separately here
     along with the modified cmdline args.
+    We also accept ... --configs <config1> <config2> ... and concatenate them into a single config.
     """
-    if "--config_path" not in args and "--config" not in args:
+    if "--config_path" not in args and "--config" not in args and "--configs" not in args:
         return None, args
     else:
-        try:
-            config_path_index = args.index("--config_path")
-        except ValueError:
-            config_path_index = args.index("--config")
-
-        config_path = args[config_path_index + 1]
-
-        if urllib.parse.urlparse(config_path).scheme:
-            fs: AbstractFileSystem
-            fs, fs_path = fsspec.core.url_to_fs(config_path)
-            temp_file = tempfile.NamedTemporaryFile(prefix="config", suffix=".yaml", delete=False)
-            atexit.register(lambda: os.unlink(temp_file.name))
-            fs.get(fs_path, temp_file.name)
-            config_path = temp_file.name
+        config_args = ["--config_path", "--config", "--configs"]
+        found_indices = [args.index(arg) for arg in config_args if arg in args]
+        if len(found_indices) > 1:
+            raise ValueError(f"Multiple config args found in {args}")
+        config_path_index = found_indices[0] + 1
 
+        config_paths: List[str] = []
         args = args.copy()
-        del args[config_path_index]
-        del args[config_path_index]
-        return config_path, args
+        del args[config_path_index - 1]
+        config_path_index -= 1
+
+        while config_path_index < len(args) and not args[config_path_index].startswith("-"):
+
+            config_path = args[config_path_index]
+
+            if urllib.parse.urlparse(config_path).scheme:
+                fs: AbstractFileSystem
+                fs, fs_path = fsspec.core.url_to_fs(config_path)
+                temp_file = tempfile.NamedTemporaryFile(prefix="config", suffix=".yaml", delete=False)
+                atexit.register(lambda: os.unlink(temp_file.name))
+                fs.get(fs_path, temp_file.name)
+                config_path = temp_file.name
+
+            config_paths.append(config_path)
+            del args[config_path_index]
+
+        merged_config_path = None
+
+        if len(config_paths) == 1:
+            merged_config_path = config_paths[0]
+        elif len(config_paths) > 1:
+            # merge the configs by concatenating them
+            temp_merged_config_path = tempfile.NamedTemporaryFile(prefix="config_merged", suffix=".yaml", delete=False)
+            atexit.register(lambda: os.unlink(temp_merged_config_path.name))
+            with open(temp_merged_config_path.name, "w") as f:
+                for config_path in config_paths:
+                    with open(config_path) as config_file:
+                        f.write(config_file.read())
+            merged_config_path = temp_merged_config_path.name
+        else:
+            raise ValueError("No config path found in args")
+
+        return merged_config_path, args