phabricator: fix a phabsend crash when processing a renamed binary This was a trivial fix, and some more tests are added to cover binary files. Since the old filecontext is passed in, the old name is still available. But I noticed some weirdness around what it marked as binary and not, and what is viewable in Phabricator. Those things have been flagged, and will probably take some digging. Differential Revision: https://phab.mercurial-scm.org/D8133