f missing internal docs

Author: TheBlueMatt

lightning/src/chain/chainmonitor.rs

@@ -44,8 +44,15 @@ use core::ops::Deref;
 use core::sync::atomic::{AtomicBool, Ordering};
 
 #[derive(Clone, Copy, Hash, PartialEq, Eq)]
+/// A specific update stored in a `MonitorUpdateId`, separated out to make the contents entirely
+/// opaque.
 pub(crate) enum MonitorUpdate {
+	/// An update which was generated by the [`ChannelManager`] (via our `chain::Watch`
+	/// implementation). This corresponds to an actual [`ChannelMonitorUpdate::update_id`] field
+	/// and [`ChannelMonitor::get_latest_update_id`].
 	MonitorUpdateId(u64),
+	/// An update which was generated during blockchain processing. The ID here is specific to the
+	/// generating [`ChainMonitor`] and does *not* correspond to any on-disk IDs.
 	SyncPersistId(u64),
 }