f - clarify docs

Author: jkczyz

lightning/src/routing/mod.rs

@@ -19,7 +19,8 @@ use routing::network_graph::NodeId;
 ///
 ///	Scoring is in terms of fees willing to be paid in order to avoid routing through a channel.
 pub trait Score {
-	/// Returns the fee in msats willing to be paid to avoid routing through the given channel.
+	/// Returns the fee in msats willing to be paid to avoid routing through the given channel from
+	/// `source` to `destination`.
 	fn channel_penalty_msat(
 		&self, short_channel_id: u64, source: &NodeId, destination: &NodeId
 	) -> u64;