Cleanup.

src/mapping/map.rs

@@ -202,6 +202,7 @@ pub fn write_map_to_file(file: &mut File, map: &MapFile) -> anyhow::Result<usize
     Ok(written_bytes)
 }
 
+// This is split out for a shred of readability.
 fn other_engulfs_self_update(new: Cluster, old: &mut Cluster, map: &mut Vec<Cluster>) {
     if new.domain.start == old.domain.start {
         // Case 6 of map::tests::test_update
@@ -229,8 +230,6 @@ fn other_engulfs_self_update(new: Cluster, old: &mut Cluster, map: &mut Vec<Clus
 
 #[cfg(test)]
 mod tests {
-    use std::collections::HashSet;
-
     use super::*;
 
     /// Test for MapFile::update()