A short update about submodules in git.
Let’s start by adding an existing Git repository as a submodule of the repository that we’re working on. To add a new submodule you use the git submodule add command with the absolute or relative URL of the project you would like to start tracking.
git submodule add https://github.com/forcewake/CommandPipeline
By default, submodules will add the subproject into a directory named the same as the repository.
More information you can find in 7.11 Git Tools - Submodules