pyside-tools submodule not included in referential snapshot

Modern package management systems formulae/recipes such as Homebrew, Conda, etc. require a download url and companion sha to retrieve the sources from a trusted source for a build/install/packaging.  Developing a pyside-setup formula has been problematic because the pyside-tools submodules is not included in the git-archive snapshot.

For example, using the latest git sha for the 5.9 branch declared as follows, yields an empty pyside-tools directory:

  url "https://codereview.qt-project.org/gitweb?p=pyside/pyside-setup.git;a=snapshot;h=14a19ea3c2110fe8f38398b2eef81eccba7c3a9c;sf=tgz"  sha256 "421c580eda0e1adaab6ca1ee4ac46e01801552e7fa0a13bae912a19fec3b2a8a"

This can be confirmed using curl to retrieve a snapshot...

curl -L -o pyside-setup.tgz "https://codereview.qt-project.org/gitweb?p=pyside/pyside-setup.git;a=snapshot;h=14a19ea3c2110fe8f38398b2eef81eccba7c3a9c;sf=tgz"
tar xvzf pyside.tgz
cd pyside-setup/sources/pyside-tools
ls -l

This is probably just a pyside-tools submodule configuration issue because all other submodules are included in the snapshot.  See https://stackoverflow.com/a/18799234