Git Submodules
Often, software projects within your organization are not entirely self-contained, but share common components with other software projects. Git offers a submodules feature that allows you to embed one Git repository into another.
Submodules are especially useful when your organization does not use a Package Management server (such as Maven, npm, or NuGet) but requires dependency projects to be embedded or rebuilt within your solutions.
A submodule is a nested repository embedded in a dedicated subdirectory of the working tree (that belongs to the parent repository). A submodule always references a specific commit of the embedded repository. The definition of the submodule is stored as a separate entry in the parent repository’s git object database.
The link between the working tree entry and the foreign repository is stored in the .gitmodules file of the parent repository. The .gitmodules file is usually versioned so that it can be maintained and/or changes are propagated to all users.
Setting submodule repositories involves an initialization process, in which the required entries are added to the .git/config file. The user may later adjust it, for example to fix SSH login names.
Refer to Submodules in SmartGit to see how to work with Submodules inside SmartGit.