Re: git submodule add fails when using both --branch and --depth

> I'm running git 2.14.2 on Ubuntu 16.04.
>
> Compare the behavior of
>
>> git clone --branch pu --depth 1 https://github.com/git/git git-pu
>
> which clones only the latest commit of the pu branch and
>
>> mkdir tmp && cd tmp && git init
>> git submodule add --branch pu --depth 1 https://github.com/git/git \
>   git-pu
>
> which gives the error
>
> fatal: 'origin/pu' is not a commit and a branch 'pu' cannot be created
> from it
> Unable to checkout submodule 'git-pu'
>
> Investigating further, there is indeed only one commit in the local repo:
>
>> cd git-pu
>> git log --oneline | wc -l
> 1
>
> But that commit is the head of master.
>
>> git branch -a
> * master                                 remotes/origin/master
>   remotes/origin/HEAD -> origin/master
>
> This appears to be because git-submodule--helper does not accept a
> --branch option. Using the --depth N option causes it to only clone N
> commits from the default branch, which generally do not include the
> desired branch. Thus, the next step,
>
> git checkout -f -q -B "$branch" "origin/$branch"
>
> fails, and provides the rather confusing error message above.
>
> I'd suggest that git-submodule--helper learn a --branch option
> consistent with git clone, and if that is impossible, that
> git submodule add rejects the simultaneous use of both the --branch and
> --depth options.