Slightly improve prose diffs for text ending in newlines or punctuation
Summary:
Ref T3353. Currently, if text ends in newlines (or some other types of punctuation) we generate an extra piece at the end which can muck up the algorithm.
Do a slightly better job with this.
Test Plan: Viewed a diff between "a\nb\nc\n" and "a\nb\nc\nd\n", got a cleaner diff out of it.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T3353
Differential Revision: https://secure.phabricator.com/D16061