10 Git Submodule Best Practices

Git submodules are a powerful tool for managing code dependencies. They allow you to keep track of multiple repositories within a single repository, making it easier to manage and maintain code. However, they can be tricky to use and can lead to a lot of confusion if not used properly.

In this article, we’ll discuss 10 best practices for using Git submodules. We’ll cover topics such as how to set up a submodule, how to keep them up to date, and how to avoid common pitfalls. By following these best practices, you can ensure that your code is well-organized and easy to maintain.

1. Use submodules for third-party libraries

When you use a third-party library, it’s important to keep track of the version that your project is using. This ensures that if there are any changes or updates to the library, you can easily update your project accordingly. With git submodules, you can easily add and commit the library as its own repository within your main project. This way, you can always refer back to the exact version of the library that your project is using.

Additionally, when you use git submodules for third-party libraries, you don’t have to worry about including the entire library in your project. Instead, only the necessary files will be included, which helps reduce the size of your project and makes it easier to manage.

2. Don’t use submodules for your own code

Submodules are designed to be used for external code, such as third-party libraries or frameworks. When you use submodules for your own code, it can become difficult to keep track of changes and ensure that all the necessary files are included in each commit. This can lead to errors and confusion when trying to deploy your code.

Instead, it’s best to use git branches for your own code. This allows you to easily switch between different versions of your code without having to worry about managing multiple repositories. It also makes it easier to collaborate with other developers since everyone will have access to the same version of the code.

3. Avoid using nested submodules

Nested submodules can quickly become difficult to manage and maintain. When you have multiple levels of nested submodules, it becomes increasingly hard to keep track of which version of each module is being used in the project. This can lead to unexpected errors or bugs due to mismatched versions.

It’s also important to note that git does not support recursive submodule operations, so if you need to update a nested submodule, you’ll need to manually run the command for each level of nesting.

For these reasons, it’s best to avoid using nested submodules whenever possible. If you do find yourself needing to use them, make sure to document your setup thoroughly so that other developers can easily understand how everything works.

4. Keep the .gitmodules file in sync with the working tree

The .gitmodules file is a text file that contains the configuration for each submodule. It stores information such as the URL of the repository, the branch to use, and other settings. If this file gets out of sync with the working tree, then git won’t be able to properly track changes in the submodules. This can lead to unexpected behavior and errors when trying to commit or push changes.

To keep the .gitmodules file in sync, make sure you always run `git submodule update` after making any changes to the submodules. This will ensure that the .gitmodules file reflects the current state of the working tree.

5. Commit changes to a submodule only from within that submodule

When you commit changes to a submodule, the parent repository will not be aware of those changes. This means that if someone else pulls your code and tries to use it, they won’t have access to the latest version of the submodule. To ensure everyone has access to the most up-to-date version of the submodule, make sure to commit any changes from within the submodule itself.

6. Make sure everyone is on the same page

When you use git submodules, each team member needs to be aware of the changes that have been made in order for them to pull and push their own changes. This means that everyone should be familiar with the structure of the project and how it works.

It’s also important to make sure that all team members are using the same version of the submodule. If someone is using an older version, they may not be able to access the latest features or bug fixes. To ensure this doesn’t happen, it’s best practice to keep track of which versions of the submodule everyone is using.

7. Use git submodule update –remote when possible

When you use git submodule update –remote, it will fetch the latest changes from the remote repository and merge them into your local copy. This ensures that your local version of the submodule is always up-to-date with the remote version. Without this command, you would have to manually pull in any new changes from the remote repository each time you wanted to update your local version.

Using git submodule update –remote also helps ensure that all developers on a project are working off of the same version of the codebase. This can help reduce conflicts when merging branches or pushing changes.

8. Use tags instead of branches as much as you can

When you use a branch as the source for your submodule, it can be difficult to keep track of which version of the code is being used. This is because branches are constantly changing and updating, so if you don’t check in regularly, you may end up with an outdated version of the code.

On the other hand, tags provide a snapshot of the code at a specific point in time. This makes them much easier to manage and ensures that you always have access to the exact version of the code you need.

9. Consider alternatives to Git Submodules

Git Submodules can be difficult to manage and maintain, as they require extra steps when cloning or updating repositories. Additionally, submodules are not always the most efficient way of sharing code between projects.

Alternatives such as Git subtrees, which allow you to embed a repository within another one without creating a separate submodule, may be more suitable for your needs. You should also consider using package managers like NPM or Yarn if you need to share code between multiple projects.

10. Automate everything!

When you use git submodules, it’s important to keep track of all the changes that are made in each repository. This can be a tedious and time-consuming task if done manually. Automating this process ensures that all changes are tracked accurately and efficiently.

Automation also helps ensure that your code is always up-to-date with the latest version of the submodule. By automating the process, you don’t have to worry about forgetting to update the submodule or having outdated versions of the code.

Finally, automation makes it easier to manage multiple repositories at once. With automated processes, you can easily set up triggers for when certain events occur, such as when a new commit is pushed to a repository. This allows you to quickly respond to any changes without having to manually check every repository.