git.c: convert --list-* to --list-cmds=*

git.c: convert --list-* to --list-cmds=*

Even if these are hidden options, let's make them a bit more generic
since we're introducing more listing types shortly. The code is
structured to allow combining multiple listing types together because
we will soon add more types the 'builtins'.

'parseopt' remains separate because it has separate (SPC) to match
git-completion.bash needs and will not combine with others.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>