R1:437a843a8e3a

Clean up legalpad transaction copy

Summary: Ref T12685, adds more informative transaction copy, fixes bugs.

Test Plan: Create various documents and edit them.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12685

Differential Revision: https://secure.phabricator.com/D17860