[NOTE]
====
The repository contains
https://git-scm.com/book/en/v2/Git-Tools-Submodules[submodules]. Make
sure to clone with `--recursive` option in Git or by checking the
'`Recursive`' checkbox in TortoiseGit.

....
> git clone --recursive <REPO>
....

If not done when cloning, it can be done by

....
> git submodule init
> git submodule update
....
====