refactor patching logic

light_the_torch/_cli.py

@@ -1,5 +1,5 @@
-from pip._internal.cli.main import main as pip_main
+from pip._internal.cli.main import main
 
-from ._patch import patch
+from ._patch import patch_pip_main
 
-main = patch(pip_main)
+main = patch_pip_main(main)

light_the_torch/_compat.py

@@ -0,0 +1,8 @@
+import sys
+
+if sys.version_info >= (3, 8):
+    import importlib.metadata as importlib_metadata
+else:
+    import importlib_metadata
+
+__all__ = ["importlib_metadata"]

light_the_torch/_patch/__init__.py

@@ -0,0 +1 @@
+from .patch import patch_pip_main