Re: [PATCH 4/4] builtin/clone: support submodule groups

> When invocing clone with the groups option,
> the repository will be configured to the specified groups.
> This has implications for the submodule commands, such as
> update.
>
> Having groups configured will imply init for all uninitialized
> submodules belonging to at least one of the configured groups,
> such that new submodules in the group are initialized
> automatically.
>
> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  Documentation/git-clone.txt | 13 +++++++++++
>  builtin/clone.c             | 46 +++++++++++++++++++++++++++++++++++---
>  t/t7400-submodule-basic.sh  | 54 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 110 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
> index 6db7b6d..685fb7c 100644
> --- a/Documentation/git-clone.txt
> +++ b/Documentation/git-clone.txt
> @@ -214,6 +214,19 @@ objects from the source repository into a pack in the cloned repository.
>  	repository does not have a worktree/checkout (i.e. if any of
>  	`--no-checkout`/`-n`, `--bare`, or `--mirror` is given)
>  
> +--group::

> +	After the clone is created, all submodules which are part of the
> +	given groups are cloned. To specify multiple groups, you can either
> +	give the group argument multiple times or comma separate the groups.
> +	This option will be recorded in the `submodule.groups` config,
> +	which will affect the behavior of other submodule related commands,
> +	such as `git submodule update`.
> +	This option implies recursive submodule checkout. If you don't
> +	want to recurse into nested submodules, you need to specify
> +	`--no-recursive`. The group selection will be passed on recursively,
> +	i.e. if a submodule is cloned because of group membership, its
> +	submodules will be cloned according to group membership, too.
> +

>  --separate-git-dir=<git dir>::
>  	Instead of placing the cloned repository where it is supposed
>  	to be, place the cloned repository at the specified directory,
> diff --git a/builtin/clone.c b/builtin/clone.c
> index b004fb4..72aea3a 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -51,6 +51,22 @@ static struct string_list option_config;
>  static struct string_list option_reference;
>  static int option_dissociate;
>  static int max_jobs = -1;
> +static struct string_list submodule_groups;
> +
> +static int groups_cb(const struct option *opt, const char *arg, int unset)
> +{
> +	struct string_list_item *item;
> +	struct string_list sl = STRING_LIST_INIT_DUP;
> +
> +	if (unset)
> +		return -1;
> +
> +	string_list_split(&sl, arg, ',', -1);