Update default value for pythonpath ini option

Update default value for pythonpath ini option allowing to pass rootdir path for running the pytest command from within a child folder but at the same time able to resolve the path for outside modules by passing the rootdir option. Without this change unable to run pytest for a particular file within the folder if it is importing from outside the cwd, resulting in unable to find the module.

Author: rajdesai1510

src/_pytest/config/__init__.py

@@ -1518,7 +1518,7 @@ def parse(self, args: list[str], addopts: bool = True) -> None:
         self._parser.addini("addopts", "Extra command line options", "args")
         self._parser.addini("minversion", "Minimally required pytest version")
         self._parser.addini(
-            "pythonpath", type="paths", help="Add paths to sys.path", default=[]
+            "pythonpath", type="paths", help="Add paths to sys.path", default=[self._parser.extra_info["rootdir"]]
         )
         self._parser.addini(
             "required_plugins",