threads / discuss / 46864

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

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

## tl;dr

3 messages between Sep 30, 2017 and Oct 2, 2017.

replies: 2people: 3as markdown or json

Thadeus Fleming· Sep 30, 2017, 17:20 UTC · lore
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.

--tjf
Stefan Beller· Oct 2, 2017, 19:55 UTC · re: Thadeus Fleming · lore

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

On Sat, Sep 30, 2017 at 10:20 AM, Thadeus Fleming <thadeus.j.fleming@gmail.com> wrote:

Show 43 quoted lines
> 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.
Adding the branch field to the submodule helper is a great idea.
>
>
>
> --tjf
Jonathan Nieder· Oct 2, 2017, 22:08 UTC · re: Thadeus Fleming · lore

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

Hi,
Thadeus Fleming wrote:
Show 7 quoted lines
> 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
Yes.
Show 8 quoted lines
>> 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'

As a side note (you are using "git submodule add --depth", not "git submodule update --depth"), I suspect that "submodule update --depth" may not always do what people expect.

With add --depth, I agree with your expectation and after your fix everything should work fine. But with update --depth, consider the following sequence of steps:

 1. I create a repository "super" with submodule "sub" and publish
    both.
 2. I make a couple commits to "sub" and a commit to "super" making
    use of those changes and want to publish them.
 3. I use "git push --recurse-submodules" to publish my commits to
    "sub" and "super":
    a. First it pushes to "sub".
    b. Then it pushes to "super".

Between steps 3(a) and 3(b), a person can still "git clone --recurse-submodules" the "super" repository. The repository "super" does not have my change yet and "sub" does, but that is not a problem, since commands like "git checkout --recurse-submodules" and "git submodule update" know to check out the commit *before* my change in the submodule.

But between steps 3(a) and 3(b), "git submodule update --depth=1" would not work. It would fetch the submodule with depth 1 and then try to check out a commit that is deeper in history.

So I think there's more thinking needed there.
That's all a tangent to your report about add --depth, though.

Thanks, Jonathan

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