In your project, you may encounter scenarios where you add other Git repositories to one Git repository. For example, reference third-party libraries in your project. Or in modular development, where some common modules need to be maintained separately, it is convenient to use a separate repository, but need to be referenced in the project. Here you use Git’s Git submodule command to add child Git projects to a Git project.

You can use git submodule –help to see all the related commands. For the convenience of explanation, two sub-modules liba and libb are added to the MainProject MainProject.

1. Add submodules

Enter MainProject and use git submodule add to add.

cd MainProject/
git submodule add https://github.com/imtianx/liba.git
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The diagram below:

Use git submodule add https://github.com/imtianx/libb.git add libb module. For the above figure, folder liba is the newly added submodule directory,.gitModules stores the information of the submodule, use cat or vim to check the content:

[submodule "liba"]
	path = liba
	url = https://github.com/imtianx/liba.git
[submodule "libb"]
	path = libb
	url = https://github.com/imtianx/libb.git
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Gitmodules file: Saves the mapping between the project URL and the local directory that has been pulled. Multiple submodules contain multiple records that will be pulled and pushed along with version control.

The file directory tree is as follows:

. ├ ─ ─ the README. Md ├ ─ ─ liba │ ├ ─ ─ the README. Md │ ├ ─ ─ a.t xt │ └ ─ ─ a2. TXT ├ ─ ─ libb │ ├ ─ ─ the README. Md │ ├ ─ ─ b.t xt │ └ ─ ─ b2. TXT └ ─ ─ test.textCopy the code

Finally, commit the added submodule to the home directory

$ git commit -m "add liba and libb submodules"
[master 6b15e30] add liba and libb submodules
 3 files changed, 8 insertions(+)
 create mode 100644 .gitmodules
 create mode 160000 liba
 create mode 160000 libb
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2. Update submodules

Often submodules are developed separately, here is an example of updating liba (for testing purposes, a file is added in the liBA repository first) :

cd liba/
git fetch
git merge origin/master
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The following figure shows the operation result. Note that you need to enter the submodule directory:

Alternatively, you can update the libb submodule directly from your home directory with the following command:

git submodule update --remote liba
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Update using the following methodlibb 的 devBranches:

git config -f .gitmodules submodule.liba.branch dev
git submodule update --remote
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The diagram below:

-f to.gitModules, which is valid for all users after modification.

3. Delete submodules

In daily development, there is a need to add and, of course, remove submodules. Here, the main project contains two sub-modules: liba and libb. Take deleting liba as an example:

  • usegit rm --cached libaDelete liba from version control (local version still exists), if not necessary--cachedDelete it completely.
  • usevim .gitmodulesOpen Vim to edit and delete the corresponding content
 [submodule "liba"]
          path = liba
          url = https://github.com/imtianx/liba.git
          branch = dev
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  • usevim .git/configOpen Vim to edit and delete the corresponding content
[submodule "liba"]
         url = https://github.com/imtianx/liba.git
         active = true
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  • userm -rf .git/modules/liba, delete the cache module under.git, and finally submit the project.

Submodules can also be added after the above deletion.

4. Clone the warehouse with sub-modules

If you want to clone a repository containing submodules that cannot be pulled directly, add the –recursive parameter as follows:

git clone --recursive https://github.com/imtianx/MainProject.git
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Or use the following three steps:

git clone  https://github.com/imtianx/MainProject.git
git submodule init
git submodule update
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For more operations on submodules, please refer to the official documentation: Git Tools – Submodules