Gitのoriginよりも進んだブランチをどう解決するか

Introduction

In this lab, you will learn how to handle a common Git scenario: when your local branch is ahead of the remote repository. This situation occurs when you make commits locally but haven't pushed them to the remote repository yet. By the end of this lab, you will understand how to identify when your branch is ahead of the remote and how to synchronize your local and remote repositories properly.

Skills Graph

Making Local Changes

In this step, you will make changes to your local repository that haven't been pushed to the remote repository, creating the "ahead of origin" scenario.

Understanding Local and Remote Repositories

Git operates with a distributed model where each developer has a complete copy of the repository on their local machine. Changes made locally need to be explicitly synchronized with the remote repository.

Let's start by navigating to our project directory:

cd ~/project/git-ahead-demo

Now, let's check the current status of our repository:

git status

You should see output similar to this:

On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

This means your local repository is currently synchronized with the remote repository.

Creating a New File

Let's create a new file in our repository:

echo "This is a new file for our project." > new_file.txt

After creating the file, we need to add it to Git's staging area:

git add new_file.txt

Now, let's commit this file to our local repository:

git commit -m "Add new_file.txt"

You should see output confirming your commit:

[master 1a2b3c4] Add new_file.txt
 1 file changed, 1 insertion(+)
 create mode 100644 new_file.txt

Checking Branch Status

Now that we've made a local commit, let's check the status of our repository again:

git status

This time, you should see:

On branch master
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean

This message indicates that your local branch has one commit that hasn't been pushed to the remote repository yet. This is exactly the situation we wanted to create - your branch is now "ahead of origin."

Viewing Branch Differences

Now that your local branch is ahead of the remote branch, let's explore how to view the specific differences between your local and remote branches.

Understanding Branch References

In Git, you refer to the remote branch using the format origin/branch-name. The term origin is the default name for the remote repository, and branch-name is the name of the branch (in our case, it's master).

Viewing Commit Differences

To see the commits that exist in your local branch but not in the remote branch, use the following command:

git log origin/master..HEAD

The output will show you the commit(s) that are in your local branch (HEAD) but not in the remote branch (origin/master):

commit 1a2b3c4d... (HEAD -> master)
Author: LabEx User <[email protected]>
Date:   ...

    Add new_file.txt

Viewing File Differences

To see which files differ between your local and remote branches, use:

git diff --name-status origin/master..HEAD

The output should show:

A       new_file.txt

This indicates that new_file.txt was added in your local branch but doesn't exist in the remote branch.

Understanding the Difference Visualization

To see the actual content differences, you can use:

git diff origin/master..HEAD

This will show the specific changes made to each file:

diff --git a/new_file.txt b/new_file.txt
new file mode 100644
index 0000000..3b2aed8
--- /dev/null
+++ b/new_file.txt
@@ -0,0 +1 @@
+This is a new file for our project.

These commands help you understand exactly what changes are in your local branch that haven't been pushed to the remote repository yet.

Pushing Changes to Remote

Now that you understand what changes are present in your local branch, it's time to synchronize your local repository with the remote repository by pushing your changes.

Understanding Git Push

The git push command sends your local commits to the remote repository. When you push, you synchronize the remote branch with your local branch, making both branches identical.

Pushing Your Changes

To push your local commits to the remote repository, use:

git push origin master

You should see output similar to this:

Enumerating objects: 4, done.
Counting objects: 100% (4/4), done.
Delta compression using up to 2 threads
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 324 bytes | 324.00 KiB/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To /home/labex/project/remote-repo.git
   abcd123..1a2b3c4  master -> master

The output shows:

• Git counted and compressed the objects in your commit
• The changes were successfully sent to the remote repository
• The old and new commit hash identifiers
• The branch that was updated (master -> master)

Verifying the Push

Let's check the status of our repository again:

git status

Now you should see:

On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

This confirms that your local branch is now synchronized with the remote branch. The "ahead of origin" message is gone because both branches now contain the same commits.

Verifying Remote Repository Content

We can verify that our changes are now in the remote repository by examining the log of the remote branch:

git log origin/master -1

This command shows the most recent commit on the remote branch, which should now include our new file:

commit 1a2b3c4d... (HEAD -> master, origin/master)
Author: LabEx User <[email protected]>
Date:   ...

    Add new_file.txt

Notice that both HEAD -> master and origin/master point to the same commit now, confirming that both branches are synchronized.

Creating and Resolving Multiple Commits Ahead

In real-world scenarios, you might have multiple commits ahead of your remote branch. Let's create this situation and learn how to resolve it.

Making Multiple Local Commits

Let's create and commit several changes:

## Create a second file
echo "This is the second file." > second_file.txt
git add second_file.txt
git commit -m "Add second_file.txt"

## Modify the README
echo "### Additional Information" >> README.md
echo "This project demonstrates Git branch synchronization." >> README.md
git add README.md
git commit -m "Update README with additional information"

Now let's check our status:

git status

You should see:

On branch master
Your branch is ahead of 'origin/master' by 2 commits.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean

Viewing Multiple Commit Differences

Let's see what commits we have locally that aren't on the remote:

git log origin/master..HEAD --oneline

You should see your two new commits:

abcd123 Update README with additional information
efgh456 Add second_file.txt

Pushing Multiple Commits

To synchronize all your local commits with the remote repository, use the same push command:

git push origin master

The output will show both commits being pushed:

Enumerating objects: 7, done.
Counting objects: 100% (7/7), done.
Delta compression using up to 2 threads
Compressing objects: 100% (4/4), done.
Writing objects: 100% (5/5), 574 bytes | 574.00 KiB/s, done.
Total 5 (delta 1), reused 0 (delta 0)
To /home/labex/project/remote-repo.git
   1a2b3c4..abcd123  master -> master

Verifying All Commits Are Pushed

Let's check our status again:

git status

You should see:

On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

This confirms that all your local commits have been successfully pushed to the remote repository.

Summary

In this lab, you have learned how to handle situations where your local Git branch is ahead of the remote branch. You have successfully:

1. Created a local commit that put your branch ahead of the remote branch.
2. Used Git commands to view the specific differences between your local and remote branches.
3. Pushed your changes to synchronize your local and remote repositories.
4. Created multiple commits locally and pushed them all at once to the remote branch.

These skills are essential for day-to-day Git workflow, as they help you keep your local and remote repositories synchronized, which is crucial for effective collaboration in software development projects. Remember that keeping your branches synchronized regularly helps prevent conflicts and makes collaboration smoother.