I’ve spent a little more than a month working with Git now. I can honestly say that while there are many things that I like about Git, there are just as many things that I personally find to be a pain in the butt. Submodules specifically have managed to be a thorn in my side on many occasions. While the concept of submodules is simple, figuring out how to actually work with them can be a chore. I say “figuring out” because not everything about working with submodules is well documented. I’ll cover two of the more difficult things to figure out: removing and updating submodules from your repository. What are Submodules? The concept of submodules is brilliant. It essentially allows you to attach an external repository inside another repository at a specific path. In order to illustrate the value of submodules, it will probably be helpful for me to explain how I am using them. My profession is working with WordPress themes. Basically, I develop feature enhancements to the themes. I develop the code for these enhancements in modules that are completely contained in their own folder. This allows for the code to be easily added to other themes and also simplifies code updates/improvements as the code for specific features is consistent across all the themes that use that specific module. Each theme that we produce is kept in its own Git repository. In addition, I’ve created a separate repository for each one of these feature modules. Rather than actually putting the feature module code directly into the theme repositories, I simply add the needed feature module repositories as submodules. For example, we have a theme called FlexxBold. FlexxBold currently includes a total of seven submodules: billboard, contact-page-plugin, featured-images, feedburner-widget, file-utility, flexx-layout-editor, and tutorials. Since I’m using submodules, the code can be pulled directly from the relevant submodule repositories rather than requiring me to manually update each individual theme repository. As I mentioned before, not everything in Git is easy to work with. There are four main functions you will need to understand in order to work with Git submodules. In order, you will need to know how to add, make use of, remove, and update submodules. I’ll cover each of those uses below. Adding Submodules to a Git Repository Fortunately, adding a submodule to a git repository is actually quite simple. For example, if I’m in the repository working directory of a new theme called SampleTheme and need to add the billboard repository to the path lib/billboard, I can do so with the following command: [user@office SampleTheme]$ git submodule add git@mygithost:billboard lib/billboard Initialized empty Git repository in ~/git_dev/SampleTheme/lib/billboard/.git/ remote: Counting objects: 1006, done. remote: Compressing objects: 100% (978/978), done. remote: Total 1006 (delta 631), reused 0 (delta 0) Receiving objects: 100% (1006/1006), 408.22 KiB, done. Resolving deltas: 100% (631/631), done.