Summary:
Fix issue where not the full sonar repo was search when looking for Diffs with a changelog entry.
(note that we don't use absolute paths as that gaves problems in the past on CI where a sparse checkout happens and the hg root turned out to be different)
Reviewed By: passy
Differential Revision: D20793800
fbshipit-source-id: a77e1602e00127ba2d831a4c6392e2f1984a4fc6
cfb77148f7