Download git submodules for tarball

Question

Is it possible to download submodules for a repository with only the working directory?

If I download a tarball of a repository from GitHub, that is equivalent to a shallow clone without the .git folder, is it at all possible to "download" the submodules into the working directory?

I tried git init && git submodule update --init, but this neither initializes nor does it update the submodules. The .gitmodules file is in the current directory.

Update: Some more background on the question: We'd like to use tarballs for checking out repositories at Travis CI, but several people use git submodules. "Don't use Git submodules" would therefore not be a good answer, but the answer doesn't really have to be something maintainable either. I just want a folder that has the code checked out and with the submodules initialized, there's no need for anything that allows me to pull down more changes later.

Answer 1

Combining a wget/tar approach, with a git init won't help you initialize submodules:

Everything is untracked after the git init.

You need to add and commit everything, before:

git submodule update --init --recursive --force

That git submodule command will then "work", but create only empty directories.
That is because the tar file didn't include the special entries (160000) created by a git submodule add.

You need to re-declare those submodules:

C:\prog\git\ReactiveCocoa-2.0-development>git submodule add --name xcconfigs https://github.com/jspahrsummers/xcconfigs.git external\xcconfigs
Cloning into 'external\xcconfigs'...
remote: Counting objects: 312, done.
remote: Compressing objects: 100% (229/229), done.
Receal 312 (delta 87), reused 306 (delta 82)
Receiving objects: 100% (312/312), 64.51 KiB | 0 bytes/s, done.
Resolving deltas: 100% (87/87), done.