Update all records already on disk by applying onEach on them.
await reddinx.localUpdate(subredditName[, options])

By default, the onEach hook is only called on records when saved on disk (either during an initial or incremental import). If you want to call it on old records as well that are outside of the incrementalWindow, you should use reddinx.localUpdate.

This will get through the list of all records already saved on disk, apply your custom onEach hook on them and update the result on disk. If onEach returns false, the existing record file will be deleted.