Re: Git submodule update remote keeps using previous default branch

[Sjoerd Langkemper <sjoerd-2021@linuxonly.nl>]

The submodule is updated according to where `origin/HEAD` points. The
`origin/HEAD` ref of a repository is not automatically updated when
the upstream default branch changes. However, this can be forced with
`git remote set-head origin -a`.

I think it is a little bit surprising that `origin/HEAD` does not
necessarily point to the remote default branch. However, changing the
default branch should be pretty rare, so I understand this is not
checked every time.

Regards,

Sjoerd Langkemper

On Fri, Oct 15, 2021 at 10:34 AM Sjoerd Langkemper
<sjoerd-2021@linuxonly.nl> wrote:
>
> I am having trouble with git 2.33.1 checking out the wrong branch for
> submodules for which the default branch has changed. `git submodule
> update --remote` seems to remember the branch name to retrieve, while
> I expect it to use the remote HEAD every time. This causes unexpected
> behaviour when the remote HEAD starts pointing to another branch.
>
> I create a new git project and add a submodule, with `git submodule
> add git@host:foo/testproject.git`.
>
> This checks out the default branch, `master` in this case. `git remote
> show origin` also shows that `master` is the HEAD branch. Running `git
> submodule update --remote` updates the submodule to the latest master.
>
> Now I change the default branch on the remote (using Gitlab's web
> interface) to `newmaster`.
>
> `git remote show origin` now correctly shows `newmaster` as the
> remote's HEAD branch. However, running `git submodule update --remote`
> still updates the submodule to the latest `master` branch, while I
> expect it to update to the lastest `newmaster` branch.
>
> There's no branch specified in .gitmodules or .git/config. I am not
> sure how git remembers the branch. When switching `testproject` to
> `newmaster` manually and then running `git submodule update --remote`,
> it is reset to `master` again.
>
> Is this a bug? Can I change the branch somehow?
>
> Regards,
>
> Sjoerd Langkemper