Fixed jump nav repo functionality to not mess with other jump nav functionality

Summary: just changed the regex to only look at the beginning of the string

Test Plan: works with: s PhabricatorDAO, rP, r,
rPda892bde7c6e9c8f08572fde2d55c934f26dbb86

Reviewers: epriestley

Reviewed By: epriestley

CC: ddfisher, aran, epriestley

Differential Revision: https://secure.phabricator.com/D1703