Summary: Depends on D20838. Fixes T13414. Instead of doing coarse diffing with "PhutilEditDistanceMatrix", use hash-and-diff with "DocumentEngine".
Test Plan:
- On a large document (~3K top level blocks), saw a more sensible diff, instead of the whole thing falling back to "everything changed" mode.
- On a small document, still saw a sensible granular diff.
{F6888249}
Maniphest Tasks: T13414
Differential Revision: https://secure.phabricator.com/D20839
884cd74cc4