Before this fix rclone v1.51 and 1.52 would incorrectly use the cached
root_folder_id when the --drive-impersonate flag was in use. This
meant that rclone could be looking up the wrong directory ID with
unpredictable results - usually all files apparently being missing.
This fix makes rclone look up the root_folder_id always when using
--drive-impersonate. It does this by clearing the root_folder_id and
making a NOTICE message that it is ignoring the cached value.
It also stops rclone caching the root_folder_id when using
--drive-impersonate.
See: https://forum.rclone.org/t/rclone-gdrive-no-longer-returning-anything/17215
37308832b1