An alternative to submodules is subtree merging. Subtree merging is a strategy that can be used while performing merges with Git. The subtree merge strategy is useful when merging a branch (or as we'll see in this recipe another project) into a subdirectory of a Git repository instead of the root directory. When using the subtree merge strategy, the history of the subproject is joined with the history of the super project, while the subproject's history can be kept clean except for commits indented to go upstream.

$ git clone https://github.com/dvaske/super.git
$ cd super

$ git remote add lib_a git://github.com/dvaske/lib_a.git
$ git fetch lib_a
warning: no common commits
remote: Reusing existing pack: 18, done.
remote: Total 18 (delta 0), reused 0 (delta 0)...