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Submodules are a way to keep a Git repository as a subdirectory in the current branch. Submodules are usually imported from third-party repositories. For example, a large project might have a submodule that contains a library.

submoduleCan be used for any part of a project. It can have its submodules and so on, depending on the requirement. They are Git repositories in a parent Git repository fixed at a specific path in the working directory of the parent repository.

To develop submodules, we git submodule initcreate a file in the root directory of our project .gitmoduleswith that contains a list of the submodules we intend to use in the next tasks. We will then use the command git submodule updateto pull in our submodules.

To update a submodule, we should specify the submodule path in the parent repository. To access a submodule, we must always specify the path relative to the parent repository. Therefore, the submodule path is relative to the project.

To avoid the need to specify the submodule path, we can gitmodulesset the submodule path in a gitmodules./opt gitmodules...

Updating Git submodules

We'll show you how to update a Git submodule in our workspace with the most recent commit on the server.

• Clone the remote repository if we haven't already.

• Issue a git submodule update -remotecommand.

• Lists any new files pulled from the repository into the Git index.

• Perform a git commit.

• Push back to the origin.

git submoduleThe command has a --updateparameter called that can be used to get the latest code from a submodule.

git submodule --update 

SomeSubmodule $ git submodule --sync

SomeSubmodule $ git submodule update --init 

We can updateupdate the submodule to the latest commit using the -p alias. To avoid a lot of complicated checkout and push commands, it is much simpler to create a quick alias for the submodule update command.

git submodule update --remote --merge

The above command updates all submodules, making sure the working tree is clean and in sync with the remote branch. To avoid getting a merge commit every time, use -mergethe -p flag to merge updates. Using Git submodulesis like a double-edged sword, because it can make our development life easier, but it can also make our life harder if we don't know how it works. The more we use it, the more we understand how they work and thus be able to use them to our advantage.