Git does not see the folder in the repository, how to initialize it?

Question

git

The bottom line is that I have a site, on the site a link to another site, which is located in the same folder.
When uploading a shared folder to git, he sees the folder with the "subsite" as empty. The question is: why is this and how to fix it? (highlighted in blue is the folder that git fills as empty)

Answer 1

https://git-scm.com/book/en/v1/Tools-Git-Under...
git submodule init