Scenario:

You have a Git repository at /home/interview/repo that contains a submodule in the vendor/utils directory. The submodule is pointing to an old commit, but newer commits exist on the submodule's remote repository.

Task:

Update the submodule to the latest commit on its default branch and commit this change in the parent repository.

Example:

# Before (submodule at old commit)
$ git submodule status
 a1b2c3d vendor/utils (v1.0.0)

$ cd vendor/utils && git log --oneline -1
a1b2c3d Add helper function

# After (submodule updated)
$ git submodule status
 e5f6g7h vendor/utils (v1.2.0)

$ cd vendor/utils && git log --oneline -1
e5f6g7h Add advanced features

Step 1: Navigate to the repository and check submodule status

cd /home/interview/repo
git submodule status

See the current commit hash the submodule is pointing to.

Step 2: Check if submodule is behind remote

cd vendor/utils
git fetch origin
git log --oneline HEAD..origin/main

Shows what new commits are available on the remote that aren't in the current submodule.

Step 3: Pull latest changes in submodule

git pull origin main
git log --oneline -1

Updates the submodule to the latest commit and verifies the new commit hash.

Step 4: Return to parent repository and check status

cd ../..
git status

Should show vendor/utils as modified since the submodule now points to a new commit.

Step 5: View the submodule change

git diff vendor/utils

Shows the submodule commit reference change (old hash → new hash).

Step 6: Commit the submodule update

git add vendor/utils
git commit -m "Update vendor/utils submodule to latest version"

Stages and commits the new submodule reference to the parent repository.

Step 7: Verify the update

git submodule status

Confirms the submodule is now at the updated commit.