feat: add mark_saved

rust/automerge/src/automerge.rs

@@ -792,6 +792,11 @@ impl Automerge {
         bytes
     }
 
+    /// Mark the document as saved
+    pub fn mark_saved(&mut self) {
+        self.saved = self.get_heads();
+    }
+
     /// Save the changes since the last call to [Self::save`]
     ///
     /// The output of this will not be a compressed document format, but a series of individual

rust/automerge/src/change.rs

@@ -112,6 +112,17 @@ impl Change {
         self.stored.iter_ops()
     }
 
+    pub fn difference(&self) -> (u32, u32) {
+        self.iter_ops()
+            .map(|op| match op.action {
+                1 => (1, 0),
+                3 => (0, 1),
+                _ => (0, 0),
+            })
+            .reduce(|acc, x| (acc.0 + x.0, acc.1 + x.1))
+            .unwrap_or_default()
+    }
+
     pub fn extra_bytes(&self) -> &[u8] {
         self.stored.extra_bytes()
     }