See https://www.facebook.com/phabricator/posts/180013725456604

When a file moves, we currently track it as far back as the move:

https://secure.phabricator.com/diffusion/P/history/master/src/applications/differential/controller/DifferentialDiffCreateController.php

...but don't give you an easy way to continue beyond the move. We should continue history (probably with some clear demarcation between the locations) or at least give you a button to jump to the other location's history.