Working with Git Submodules

Git submodules enable you to have repositories inside of each other, this can be a useful mechanism to share code between projects.

Adding a submodule to a project
git submodule init
git submodule add [url] (you can use git submodule init [url] [foldername] to specify folder)

Where [url] is the location of the git repository.

git add -A
git commit -m "Add submodules"
(then push if you want to share!)

This will add a reference to a specific commit to the project.

Downloading submodules in a repository that already has them setup
Clone the repository as normal
git clone [url]

Then init/update the submodules
git submodule init
git submodule update

If you haven't already cloned you can do
git clone --recursive-submodules [url]

updating the submodule
cd into the modules folder
cd mysubmodule

Then use normal git operations, i.e. pull
git pull

then cd back to the main repository and commit the update
git add -A
git commit -m "updated submodule"

Reset submodule to the commit stored in the parent
git submodule update

This will checkout the specific commit that is stored in the parent repository.

Changes in the submodule
When in the submodule folder you can make changes to the modules repository using normal git commands. Just make sure you push then add/commit in the parent repository so that everyone else gets the changes when they do submodule update.

Automatically updating submodules on git pull
You can git to automatically update submodules by adding the following setting to gits config (you could also just set this per repository)

git config submodule.recurse true