Summary: Ref T13559. If you create comments A and B, then delete comments A and B, then undo the deletion of A, the UI undoes the deletion of B instead. This is becasue the undo rows are shipped down with a static scalar metadata reference. When copied multiple times to create multiple undo rows, they reference the same data object. Preventing this in the general case is a problem with greater scope. For now, just avoid rendering these rows with any metadata so they don't alias a single data object. Test Plan: - Created comments A, B. - Deleted comments A, B. - Clicked "Undo" on A. - Before: Deletion of "B" undone. - After: Deletion of "A" undone. Maniphest Tasks: T13559 Differential Revision: https://secure.phabricator.com/D21650