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

which clones only the latest commit of the pu branch and

  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:

1

But that commit is the head of master.

* 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.

--tjf