Fetching Changes from a Remote (git fetch)

While commands like git clone get a complete copy of a remote repository initially, and git push sends your local changes to the remote, you also need a way to bring down changes made by others from the remote repository into your local copy without immediately merging them into your working files. This is precisely the function of the git fetch command.

Think of git fetch as checking your project's mailbox. It goes to the specified remote repository (commonly named origin) and downloads any data that you don't have locally. This includes new commits, new branches, and updates to existing branches that have occurred on the remote since your last communication.

However, and this is an important distinction, git fetch only downloads this new data. It places the updates into your local repository database but does not automatically merge them into your local working branches (like main) or modify your working directory. Your current work remains untouched.

How git fetch Updates Your Local Repository

When you run git fetch, Git performs these main actions:

1. Connects: It contacts the remote repository you specify (or the default origin if none is specified).
2. Downloads Data: It identifies any commits and associated files present on the remote but missing from your local repository and downloads them.
3. Updates Remote-Tracking Branches: This is the primary way git fetch makes the downloaded information accessible. For each branch on the remote (like main), Git updates a corresponding remote-tracking branch in your local repository. These act like bookmarks, remembering the state of the remote branches the last time you fetched. They follow the naming convention <remote_name>/<branch_name>, for example, origin/main, origin/feature-x, etc. These branches are local references, but you cannot directly edit them; Git moves them automatically when you fetch.

Running the Command

The most common way to use fetch is:

git fetch <remote_name>

For instance, to fetch all updates from the default remote repository named origin, you would run:

git fetch origin

If you have multiple remotes configured, you would specify the one you want to fetch from. If you simply run git fetch without specifying a remote name, Git will typically fetch from origin if it exists and is configured as the default.

Viewing Fetched Changes

Since git fetch doesn't modify your working branches (like main), how do you see what changes were brought down? You compare your local branch with the updated remote-tracking branch.

For example, after running git fetch origin, you can see the commits that are on origin/main but not yet in your local main branch using git log:

# Shows commits on origin/main that aren't on your local main yet
git log main..origin/main

# You can also view a summary of changes
git log --oneline --graph --decorate main..origin/main

To see the combined differences (like a patch) between your local main and the fetched origin/main:

# Shows the actual code changes between the two branches
git diff main..origin/main

This diagram illustrates how git fetch updates the local origin/main reference to match the state of main on the remote. Integrating these changes into the local main branch requires a separate git merge command.

Why Use git fetch Instead of git pull?

You might wonder why you'd use git fetch if git pull (which we'll cover next) often fetches and merges in one step. Using git fetch provides a safer workflow, especially in complex projects:

• Review Before Merging: It allows you to inspect the incoming changes (git log origin/main, git diff origin/main) before integrating them into your local work. This helps you understand the changes and anticipate potential conflicts.
• Control Over Integration: You decide when and how to integrate the fetched changes (e.g., using git merge or git rebase).
• Updating Multiple Branches: Fetch brings down updates for all branches from the remote, allowing you to see the state of various feature branches without checking them out locally.

In summary, git fetch is the command you use to download the latest information from a remote repository into your local Git database, updating your remote-tracking branches. It's a fundamental command for staying synchronized with remote collaborators without immediately altering your own local development branches. The next step after fetching is often to integrate those changes, typically using git merge.