Symphony.

Hello, I cloned a branch of Symphony from Github. It has an array of folders under extensions/, which are empty.
Since I understand that being made for better assets management, is there a git command for filling them up with the corresponding content? Submodules? And if I want to add further, is there a command for adding extensions without breaking the manifest? I know little of git, I guess a cloning within a repository might be unelegant.

Thanks for any suggestion

This just happened to me again on a fresh 2.6.2 installation using the instructions on Github.

I had to replace git:// with https:// in /.git/config for step 2 on submodules to work as expected.