merge-ort: fix slightly overzealous assertion for rename-to-self

merge-ort has a number of sanity checks on the file it is processing in process_renames(). One of these sanity checks was slightly overzealous because it indirectly assumed that a renamed file always ended up at a different path than where it started. That is normally an entirely fair assumption, but directory rename detection can make things interesting. As a quick refresher, if one side of history renames directory A/ -> B/, and the other side of history adds new files to A/, then directory rename detection notices and suggests moving those new files to B/. A similar thing is done for paths renamed into A/, causing them to be transitively renamed into B/. But, if the file originally came from B/, then this can end up causing a file to be renamed back to itself. It turns out the rest of the code following this assertion handled the case fine; the assertion was just an extra sanity check, not a rigid precondition. Therefore, simply adjust the assertion to pass under this special case as well. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>