This is where Git submodules<\/strong> come into play. A Git submodule<\/strong> is a reference to a specific commit in another Git repository. Git Submodules<\/a><\/p>\n Before proceeding, you may find it useful to check out a couple of related posts from our team that explore similar challenges. For instance, one covers how to synchronize an open-source project hosted on GitHub<\/a>, and a private downstream mirror Azure Repos<\/a>. More information here: Synchronizing multiple remote Git Repositories – ISE Developer Blog<\/a>. Or this post which addresses a common dilemma faced when working with shared NuGet packages across multiple solutions\u2014specifically, whether to manage them in a mono-repo or micro-repo setup. You can find more information here: Developing with Multiple Repositories inside a Single Solution for .NET<\/a><\/p>\n Now, back to the scenario at hand.<\/p>\n Fig 1 – Submodule:<\/strong>\nDemonstrates how Repository A includes a defined part of Repository B as a submodule, enabling controlled updates and modular development.<\/p>\n Fig 1 – Submodule.<\/p>\n In this post, we\u2019ll explore how Git submodules can help efficiently manage such scenarios. As a bonus at the end, we\u2019ll also show how to build GitHub Actions on top of this.<\/p>\n To include a subset of another repository into your project using Git submodules, follow the steps below:<\/p>\n From the main repository\u2014Repository A<\/strong> in Fig. 1\u2014you can add Repository B<\/strong> as a submodule. This allows you to include another Git repository inside your current one. In this example, we\u2019re adding Repository B ( To do this, use the following command:<\/p>\n Example:<\/p>\n This fetches the content of the submodule and initializes any nested submodules if present:<\/p>\n (Optional, but helpful if the submodule is already cloned and you want the latest changes.)<\/p>\n Navigate into the submodule folder and view the commit history to select the specific revision you want:<\/p>\n In this example it would be Note:<\/strong> Copy the desired commit hash.<\/p><\/blockquote>\n Use the commit hash from the previous step:<\/p>\n Move back to the root of your main repository and stage the submodule at the chosen commit:<\/p>\n Finally, push your main repository with the submodule reference included:<\/p>\n You can also add this as a GitHub Action and manually trigger updates<\/p>\n Create the following file with this structure References:<\/p>\n Using our scenario example:<\/p>\n From GitHub Actions, you should be able to see the workflow and run it, as shown in Fig 2:<\/p>\n Fig 2 – Workflow.<\/p>\n Inside of the Submodule folder if everything worked, it should show something similar to the Fig 3 – Results:<\/p>\n Fig 3 – Results.<\/p>\n![\"Fig1_submodule\"](\"https:\/\/devblogs.microsoft.com\/ise\/wp-content\/uploads\/sites\/55\/2025\/10\/Fig1_submodule.png\")
<\/p>\nStep-by-Step: Adding a Git Submodule at a Specific Revision<\/h3>\n
\n1. Add the Submodule<\/h4>\n
https:\/\/github.com\/youruser\/test.git<\/code>) into Repository A (https:\/\/github.com\/youruser\/ExampleGit.git<\/code>). Please note, those two repositories names are just random examples, they do not exist.<\/p>\ngit submodule add -b <branch> <repo-url> <path><\/code><\/pre>\n\n
<branch><\/code> with the branch you want to track in the submodule.<\/li>\n<repo-url><\/code> with the URL of the submodule repository (e.g., https:\/\/github.com\/youruser\/test.git<\/code>).<\/li>\n<path><\/code> with the folder name where the submodule should be placed in Repository A (e.g., submoduletest\/test<\/code>).<\/li>\n<\/ul>\ngit submodule add -b main https:\/\/github.com\/youruser\/test.git submoduletest\/test<\/code><\/pre>\n<\/blockquote>\n2. Initialize and Update the Submodule<\/h4>\n
git submodule update --init --recursive<\/code><\/pre>\n
\n3. Fetch the Latest Changes<\/h4>\n
git fetch<\/code><\/pre>\n
\n4. Check the Commit Log of the Submodule<\/h4>\n
cd submoduletest\/test<\/code><\/p>\ncd path_to_the_submodule\r\ngit log --online<\/code><\/pre>\n
\n5. Checkout the Specific Commit<\/h4>\n
git checkout <commit-hash><\/code><\/pre>\n
\n6. Stage and Commit the Submodule Reference<\/h4>\n
cd ..\r\ngit add path_to_the_submodule\r\ngit commit -m \"Add submodule at specific revision\"<\/code><\/pre>\n
\n7. Push the Changes<\/h4>\n
git push<\/code><\/pre>\n\n
\n
Example GitHub Action (in main repo)<\/h3>\n
.github\/workflows\/update-submodule_OR_ANY_OTHER_NAME.yml<\/code>:<\/p>\nmain-repo\/\r\n\u251c\u2500\u2500 .github\r\n\u2514\u2500\u2500\u2500\u2500 workflows\/<\/code><\/pre>\n\n
name: Manual Submodule Update_v2 (branch)\r\n\r\non:\r\n workflow_dispatch: \r\n\r\npermissions:\r\n contents: write\r\n\r\njobs:\r\n update-submodule:\r\n runs-on: ubuntu-latest\r\n\r\nsteps:\r\n - name: Checkout main repo with submodules\r\n uses: actions\/checkout@v4\r\n with:\r\n submodules: recursive\r\n token: ${{ secrets.GITHUB_TOKEN }}\r\n\r\n - name: Update submodule 'test' to latest \r\n run: |\r\n cd submoduletest\/test\r\n git checkout main\r\n git pull origin main\r\n cd ..\/..\r\n \u00a0\u00a0\u00a0\u00a0\u00a0git config user.name \"github-actions[bot]\"\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0git config user.email \"github-actions[bot]@users.noreply.github.com\"\r\n git add submoduletest\/test\r\n git commit -m \"Manually triggered: update submodule 'test' to latest\" || echo \"No changes to commit\"\r\n git push origin HEAD:main \r\n<\/code><\/pre>\n![\"Fig2_Workflow\"](\"https:\/\/devblogs.microsoft.com\/ise\/wp-content\/uploads\/sites\/55\/2025\/10\/Fig2_Workflow.png\")
<\/p>\n![\"Fig3_WorkflowResults\"](\"https:\/\/devblogs.microsoft.com\/ise\/wp-content\/uploads\/sites\/55\/2025\/10\/Fig3_WorkflowResults.png\")
<\/p>\nWhat This Workflow Does<\/h3>\n