2024/06/17

That you can use the .gitmodules document in the parent repo to configure a submodule to track a branch with the same name as the parent repo’s current branch:

submodule..branch

[…] A special value of . is used to indicate that the name of the branch in the submodule should be the same name as the current branch in the current repository.

– https://git-scm.com/docs/gitmodules#Documentation/gitmodules.txt-submoduleltnamegtbranch