When some operations are interrupted (or "die()'d" or crashed) then the
partial object/pack/index file may remain around. Make it more obvious
in their name that those files are temporary stuff and can be cleaned up
if no operation is in progress.
Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>