Fix a possible fatal on the first push to a cluster repository
Summary:
Fixes T11020. I think this resolves things -- `$new_version` (set above) should be used, not `$new_log` directly.
Specifically, we would get into trouble if the initial push failed for some reason (working copy not initialized yet, commit hook rejected, etc).
Test Plan: Made a bad push to a new repository. Saw it freeze before the patch and succeed afterwards.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T11020
Differential Revision: https://secure.phabricator.com/D15969