format-patch/log/whatchanged all take --not and --all as options
to the internal revlist process. So these should be supported
as possible completions.
gitk takes anything rev-list/log/whatchanged takes, so we should
use complete_revlist to handle its options.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>