====== submodules ======
git submodules are entire projects that are incorporated into another project.  These submodules maintain their own version history.  The most important point to understand is that when working with a submodule, you are only doing the following:
  - telling the master project what to call the submodule (a directory name)
  - telling the master project where to pull this submodule project from (a repo location)
  - telling the master project which SHA-1 hash (revision number) of this submodule will be used in the master project

===== adding a submodule =====
<code>
git submodule add /path/to/submodule.git path/for/submodule/in/your/project
(adds a folder for the submodule, and creates .gitmodules at the root of your project)

git submodule init
(adds the submodule reference info from .gitmodules to your .git/config)

git submodule update
(checks out the submodule)
</code>

===== removing a submodule =====
  - Delete the relevant line from the .gitmodules file.
  - Delete the relevant section from .git/config.
  - Run git rm --cached path_to_submodule (no trailing slash).
  - Commit and delete the now untracked submodule files.

Source: http://stackoverflow.com/questions/1260748/how-do-i-remove-a-git-submodule

===== cloning a project that has submodules =====
The easiest way to clone a project with submodules is to use the %%--recursive%% flag, which initializes and checks out all submodules.<code>
git clone --recursive /path/to/repo.git

or

git clone --recursive /path/to/repo.git myproject
</code>