Fix issue with ref/fixes in commit messages

Summary: Fixes T4600. If there's also a revision, the variable "$message" gets overwritten. groan~

Test Plan: Pushed a commit with "Fixes T123" and a revision, saw it parse on the first try.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: chrisbolt, aran, epriestley

Maniphest Tasks: T4600

Differential Revision: https://secure.phabricator.com/D8519