completion: collapse extra --no-.. options

completion: collapse extra --no-.. options

The commands that make use of --git-completion-helper feature could
now produce a lot of --no-xxx options that a command can take. This in
many case could nearly double the amount of completable options, using
more screen estate and also harder to search for the wanted option.

This patch attempts to mitigate that by collapsing extra --no-
options, the ones that are added by --git-completion-helper and not in
original struct option arrays. The "--no-..." option will be displayed
in this case to hint about more options, e.g.

    > ~/w/git $ git clone --
    --bare                 --origin=
    --branch=              --progress
    --checkout             --quiet
    --config=              --recurse-submodules
    --depth=               --reference=
    --dissociate           --reference-if-able=
    --filter=              --separate-git-dir=
    --hardlinks            --shallow-exclude=
    --ipv4                 --shallow-since=
    --ipv6                 --shallow-submodules
    --jobs=                --shared
    --local                --single-branch
    --mirror               --tags
    --no-...               --template=
    --no-checkout          --upload-pack=
    --no-hardlinks         --verbose
    --no-tags

and when you complete it with --no-<tab>, all negative options will be
presented:

    > ~/w/git $ git clone --no-
    --no-bare                 --no-quiet
    --no-branch               --no-recurse-submodules
    --no-checkout             --no-reference
    --no-config               --no-reference-if-able
    --no-depth                --no-separate-git-dir
    --no-dissociate           --no-shallow-exclude
    --no-filter               --no-shallow-since
    --no-hardlinks            --no-shallow-submodules
    --no-ipv4                 --no-shared
    --no-ipv6                 --no-single-branch
    --no-jobs                 --no-tags
    --no-local                --no-template
    --no-mirror               --no-upload-pack
    --no-origin               --no-verbose
    --no-progress

Corner case: to make sure that people will never accidentally complete
the fake option "--no-..." there must be one real --no- in the first
complete listing even if it's not from the original struct option.

PS. This could could be made simpler with ";&" to fall through from
"--no-*" block and share the code but ";&" is not available on bash-3
(i.e. Mac)

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