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Update Git Submodules — Latest Commit, Rollback, Branch Tracking & Sync

In the previous post, we cloned a repository that contains submodules and initialized them correctly.
Now let’s learn how to:

Update a submodule to the latest commit of its tracked branch
Commit that pointer change in the parent repo
Roll back to a previous commit if needed
Add a submodule that tracks a specific branch
Sync URLs when a submodule moves (e.g., GitHub → GitLab)
Handle updates with --merge or --rebase

1) Update a submodule to the latest commit

If the submodule repository (e.g., logger) received new commits and you want them:

# Update all submodules to their latest remote-tracked commits
git submodule update --remote

Update only one submodule:

git submodule update --remote logger

If your team prefers a strategy on local changes inside the submodule, add one:

# Merge remote changes into local submodule worktree
git submodule update --remote --merge logger

# Or rebase your local submodule work on top of remote
git submodule update --remote --rebase logger

After the update, your parent repo sees the submodule pointer changed:

git status
# shows: modified: logger (new commits)
git add logger
git commit -m "logger: bump to latest version"
git push origin main

👉 GitHub will now show the submodule at the new commit. Your parent project remains pinned to this exact submodule commit until you change it again.

Visual: pointer moves forward

2) Roll back the submodule to a previous commit

If the latest version introduces breaking changes and you need to revert:

# Enter the submodule
cd logger
git log --oneline          # find the older good commit (e.g., abc123)
git checkout abc123        # detach to that commit
cd ..

# Record the pointer change in the parent repo
git add logger
git commit -m "logger: roll back to abc123"
git push origin main

Now the parent repo pins logger at the older (known-good) commit.

3) Track a specific branch when adding a submodule

By default, submodules point to a commit. You can also declare which branch to track for --remote updates:

git submodule add -b submodule git@github.com:user/test-git-hook.git git-test-hook

This writes the branch into .gitmodules:

[submodule "git-test-hook"]
    path = git-test-hook
    url = git@github.com:user/test-git-hook.git
    branch = submodule

Commit the metadata:

git add .gitmodules git-test-hook
git commit -m "add submodule tracking 'submodule' branch"
git push origin main

Later, git submodule update --remote will pull from that declared branch.

4) Keep `.gitmodules` and `.git/config` in sync

Sometimes the submodule URL changes (e.g., GitHub → GitLab). You update the URL in .gitmodules, but your local .git/config still points to the old location.

Sync them:

git submodule sync
# or for a single submodule
git submodule sync -- git-test-hook

Verify:

cat .git/config        # now shows the new URL under [submodule "..."]

5) Common update flows

With conflicts/local edits inside the submodule? Use --merge or --rebase to integrate cleanly before committing the new pointer.

6) Quick commands reference

# Update all submodules to their latest tracked commits
git submodule update --remote

# Update only one submodule
git submodule update --remote logger

# Merge or rebase during update
git submodule update --remote --merge  logger
git submodule update --remote --rebase logger

# Roll back to an older commit (inside submodule worktree)
cd logger
git checkout <old-commit>
cd ..
git add logger
git commit -m "logger: roll back to <old-commit>"
git push

# Add a submodule tracking a specific branch
git submodule add -b submodule <URL> git-test-hook

# Sync .gitmodules → .git/config after URL change
git submodule sync

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