Updating submodules in Git - Step-by-Step Execution

Process Flow - Updating submodules

Start in main repo

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Run git submodule update

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Check submodule config

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Fetch latest commit for submodule

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Checkout submodule to recorded commit

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Submodule updated

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End

This flow shows how Git updates submodules by fetching and checking out the commit recorded in the main repository.

Execution Sample

Git

git submodule update --remote
# Updates submodules to latest commit on their tracked branch

This command updates all submodules to the latest commit on their configured remote branch.

Process Table

Step	Command	Action	Submodule Commit Before	Submodule Commit After	Output
1	git submodule update --remote	Start update process	abc1234	abc1234	Fetching submodule updates...
2	git fetch origin	Fetch latest commits from submodule remote	abc1234	abc1234	From https://repo.url * branch 'main' -> FETCH_HEAD
3	git checkout origin/main	Checkout latest commit on tracked branch	abc1234	def5678	Note: checking out 'def5678'
4	Update complete	Submodule now at latest commit	abc1234	def5678	Submodule updated to def5678
5	End	No more updates	def5678	def5678	Update finished successfully

💡 Submodule commit updated from abc1234 to def5678, matching latest remote commit.

Status Tracker

Variable	Start	After Step 2	After Step 3	Final
submodule_commit	abc1234	abc1234	def5678	def5678

Key Moments - 2 Insights

Why does the submodule commit change after step 3?

Because 'git checkout origin/main' moves the submodule to the latest commit on the remote branch, updating it from the old commit (abc1234) to the new one (def5678) as shown in execution_table row 3.

What happens if you run 'git submodule update' without --remote?

It will checkout the commit recorded in the main repo, not necessarily the latest remote commit. This means the submodule commit might not change, unlike in the execution_table where --remote fetches and updates.

Visual Quiz - 3 Questions

Look at the execution table, what is the submodule commit after step 2?

A def5678

B abc1234

C origin/main

D FETCH_HEAD

💡 Hint

Check the 'Submodule Commit After' column for step 2 in the execution_table.

At which step does the submodule commit update to the latest remote commit?

A Step 1

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Submodule Commit After' column and see when it changes from abc1234 to def5678.

If you omit '--remote' in the update command, how would the submodule commit change?

A It would stay at the commit recorded in the main repo

B It would update to the latest remote commit anyway

C It would reset to an earlier commit

D It would delete the submodule

💡 Hint

Refer to key_moments explanation about the difference between 'git submodule update' and 'git submodule update --remote'.

Concept Snapshot

git submodule update --remote
- Fetches latest commits for submodules
- Checks out submodules to latest remote branch commit
- Updates submodule commit pointer
- Without --remote, updates to recorded commit only
- Use to keep submodules in sync with their repos

Full Transcript

This visual execution shows how the 'git submodule update --remote' command updates submodules. Starting from the main repo, the command fetches the latest commits from the submodule's remote repository. Then it checks out the submodule to the latest commit on the tracked branch, updating the submodule commit from an old commit (abc1234) to a new one (def5678). The process ends with the submodule updated successfully. Key points include understanding that without --remote, the submodule only updates to the commit recorded in the main repo, not the latest remote commit. The variable tracker shows the submodule commit changing only after the checkout step. The quiz questions reinforce these steps and differences.