[Development] What is fastest way to checkout stable branch for every submodule for qt5 repository?

[liang jian]

    I have an old clone of qt5 which have only master branch, to
update this clone I use the following command:

    git pull
    git branch stable origin/stable
    git submodule foreach --recursive 'git checkout stable'

    The third command will fail since there is no stable branch in
qtqa, I have to checkout stable branch one by one for each
sub-repository.
    Is there any faster way to do this ? I know this is a stupid
question, but I really don't know how to achieve that.