1 files changed, 13 insertions, 2 deletions
diff --git a/src/document/store.rs b/src/document/store.rs
index 2e27b44..31c4824 100644
--- a/src/document/store.rs
+++ b/src/document/store.rs
@@ -93,8 +93,19 @@ pub(crate) fn changed_by(
     hash: &automerge::ChangeHash,
     lists: InLists,
 ) -> Option<Vec<Vec<String>>> {
-    use automerge::legacy::{Key, ObjectId};
     let change = doc.get_change_by_hash(hash)?.decode();
+    Some(changed_by_decoded(doc, hash, change, lists))
+}
+
+/// [`changed_by`] of a change already decoded (`change`, whose hash is `hash`), as from
+/// the bytes it came as: what the document rebuilding it would cost spared.
+pub(crate) fn changed_by_decoded(
+    doc: &Automerge,
+    hash: &automerge::ChangeHash,
+    change: automerge::ExpandedChange,
+    lists: InLists,
+) -> Vec<Vec<String>> {
+    use automerge::legacy::{Key, ObjectId};
     let heads = [*hash];
     // Each object's path as it was after the change, and whether that is a list's (as
     // `InLists::Whole` names what is inside one).
@@ -127,7 +138,7 @@ pub(crate) fn changed_by(
         }
         paths.insert(path);
     }
-    Some(paths.into_iter().collect())
+    paths.into_iter().collect()
 }
 
 /// Whether one path is within the other (a change at either touches both).