The documentation for pack-objects describes that it creates "a packed
archive of objects", which is confusing because it may create multiple
packs if --max-pack-size is set. Update the documentation to clarify
this, and explaining in which cases such a feature would be useful.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>