Fix Clone to preserve ordering, add Changelog entry.

Author: finnbear

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - [breaking-change] `IndexMap` and `IndexSet` now require that keys implement the `core::hash::Hash`
   trait instead of the `hash32::Hash` (v0.2.0) trait
+- `HistoryBuffer` implements `Clone` and `PartialEq`.
 
 ### Fixed
 

src/histbuf.rs

@@ -244,7 +244,11 @@ where
 {
     fn clone(&self) -> Self {
         let mut ret = Self::new();
-        ret.extend(self.iter().cloned());
+        for (new, old) in ret.data.iter_mut().zip(self.as_slice()) {
+            new.write(old.clone());
+        }
+        ret.filled = self.filled;
+        ret.write_at = self.write_at;
         ret
     }
 }