Re: [RFC_PATCHv4 1/7] git submodule: teach `add` to label submodules

Stefan Beller [off-list ref] writes:

When adding new submodules, you can specify the
label(s) the submodule belongs to by giving one or more
--label arguments. This will record each label in the
.gitmodules file as a value of the key
"submodule.$NAME.label".

Having an ability to add a label when adding a brand new submodule
would be a "nice-to-have" convenience feature, but I think it is
better to start a series to add a new concept by "need-to-have"
infrastructure that is lower-level.  E.g. "git submodule label"
command that allows you to things like:

 - query the labels on a given submodule
 - add a label to a given submodule (or to a set of submodules)
 - remove a label to a given submodule (or to a set of submodules)

And with that, the user can start using the feature without having
"git submodule add --label".