Git submodule update remote keeps using previous default branch

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