Fix earlier/later missing changeset update (#1069)

Fix #1059

helix-term/src/commands.rs

@@ -1845,7 +1845,10 @@ mod cmd {
             .map_err(|s| anyhow!(s))?;
 
         let (view, doc) = current!(cx.editor);
-        doc.earlier(view.id, uk);
+        let success = doc.earlier(view.id, uk);
+        if !success {
+            cx.editor.set_status("Already at oldest change".to_owned());
+        }
 
         Ok(())
     }
@@ -1860,7 +1863,10 @@ mod cmd {
             .parse::<helix_core::history::UndoKind>()
             .map_err(|s| anyhow!(s))?;
         let (view, doc) = current!(cx.editor);
-        doc.later(view.id, uk);
+        let success = doc.later(view.id, uk);
+        if !success {
+            cx.editor.set_status("Already at newest change".to_owned());
+        }
 
         Ok(())
     }

helix-view/src/document.rs

@@ -751,19 +751,35 @@ impl Document {
     }
 
     /// Undo modifications to the [`Document`] according to `uk`.
-    pub fn earlier(&mut self, view_id: ViewId, uk: helix_core::history::UndoKind) {
+    pub fn earlier(&mut self, view_id: ViewId, uk: helix_core::history::UndoKind) -> bool {
         let txns = self.history.get_mut().earlier(uk);
+        let mut success = false;
         for txn in txns {
-            self.apply_impl(&txn, view_id);
+            if self.apply_impl(&txn, view_id) {
+                success = true;
+            }
+        }
+        if success {
+            // reset changeset to fix len
+            self.changes = ChangeSet::new(self.text());
         }
+        success
     }
 
     /// Redo modifications to the [`Document`] according to `uk`.
-    pub fn later(&mut self, view_id: ViewId, uk: helix_core::history::UndoKind) {
+    pub fn later(&mut self, view_id: ViewId, uk: helix_core::history::UndoKind) -> bool {
         let txns = self.history.get_mut().later(uk);
+        let mut success = false;
         for txn in txns {
-            self.apply_impl(&txn, view_id);
+            if self.apply_impl(&txn, view_id) {
+                success = true;
+            }
+        }
+        if success {
+            // reset changeset to fix len
+            self.changes = ChangeSet::new(self.text());
         }
+        success
     }
 
     /// Commit pending changes to history