Fix rsync_exclude for gcp credential file_mounts (skypilot-org#496)

* Fix rsync_exclude for gcp credential file_mounts

* fix comment

* address comment

Author: Michaelvll

sky/clouds/gcp.py

@@ -256,6 +256,10 @@ def check_credentials(self) -> Tuple[bool, Optional[str]]:
         return True, None
 
     def get_credential_file_mounts(self) -> Tuple[Dict[str, str], List[str]]:
-        return {
-            '~/.config/gcloud': '~/.config/gcloud'
-        }, ['~/.config/gcloud/virtenv']
+        # Excluding the symlink to the python executable created by the gcp
+        # credential, which causes problem for ray up multiple nodes, tracked
+        # in #494, #496, #483.
+        # rsync_exclude only supports relative paths.
+        # TODO(zhwu): rsync_exclude here is unsafe as it may exclude the folder
+        # from other file_mounts as well in ray yaml.
+        return {'~/.config/gcloud': '~/.config/gcloud'}, ['virtenv']