A prior commit tried to use the old index state for the old working
directory state during a UI refresh of a file.  This caused files
which were being unstaged (and thus becoming unmodified) to drop
out of the working directory side of the display, at least until
the user performed a rescan to force the UI to redisplay everything.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>