Apply the semantic patch swap.cocci to convert hand-rolled swaps to use
the macro SWAP. The resulting code is shorter and easier to read, the
object code is effectively unchanged.
The patch for object.c had to be hand-edited in order to preserve the
comment before the change; Coccinelle tried to eat it for some reason.
Signed-off-by: Rene Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>