R1:cddbe306f927

Correct a case where a single-hunk diff may incorrectly be identified as multi-hunk by the Scope engine

Summary: See PHI985. The layers above this may return `array()` to mean "one hunk with a line-1 offset". Accept either `array()` or `array(1 => ...)` to engage the scope engine.

Test Plan: See PHI985.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20363