For a normal git repo you can do:
git clone --branch 4.1.1 https://github.com/WordPress/WordPress.git . --depth 1
Which will give a WP repo at tag 4.1.1
For a submodule I did get the below but I can't figure out how to do it for just one tag.
git submodule add --depth 1 https://github.com/WordPress/WordPress.git wp
How do I checkout a submodule to 1 tag at 1 depth?
I don't mind doing a few more commands afterwards but if possible in one command even better.
TLDR: I want a submodule at a tag. Which .git(/module) folder is as small as possible.