Git Merge

Pulling to Keep up-to-date with Changes

When working as a team on a project, it is important that everyone can stay up to date.

Any time you start working on a project, you should get the most recent changes to your local copy.

With Git, you can do that with pull.

pull is actually a combination of 2 different commands:

• fetch
• merge

Lets take a closer look into how fetch, merge, and pull works.

Git Fetch

fetch gets all the change history of a tracked branch/repo.

Now we are going to create a README.md file for our repository on GitHub. It is recommended that all repositories have a readme file, and that it describes the repository.

And commit:

Head back to your local Git, and fetch updates:

git fetch origin
remote: Enumerating objects: 4, done.
remote: Counting objects: 100% (4/4), done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 0), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (3/3), 806 bytes | 4.00 KiB/s, done.
From https://github.com/w3schools-test/hello-world
   9ab23f8..a7cdd4b  main       -> origin/main

Now that we have the recent changes, we can check our status:

git status
On branch main
Your branch is behind 'origin/main' by 1 commit, and can be fast-forwarded.
  (use "git pull" to update your local branch)

nothing to commit, working tree clean

We are behind the origin/main by 1 commit. That should be the included README.md, but lets double check by viewing the log:

git log origin/main
commit a7cdd4bf8f851b8de08d8b26be4ec82b371f4b48 (origin/main)
Author: w3schools-test <[email protected]>
Date:   Thu Mar 25 11:41:24 2021 +0100

    Created Readme.md

commit 9ab23f8e199880def2dfa775ae4868839d999747 (HEAD -> main)
Merge: 4068962 aad81e1
Author: w3schools-test <[email protected]>
Date:   Tue Mar 23 15:15:21 2021 +0100

    Merge pull request #2 from w3schools-test/new-style

    New style looks good
...
...

That looks as expected, but we can also verify by showing the differences between our local main and origin/main:

git diff main...origin/main
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..f43f0fc
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# hello-world
+Hello World repository for Git tutorial
+This is an example repository for the Git tutoial on https://www.w3schools.com

That looks precisely as expected! Now we can safely merge.

Git Merge

merge combines the current branch, with a specified branch.

We have confirmed that the updates are as expected, and we can merge our current branch (main), with origin/main:

git merge origin/main
Updating 9ab23f8..a7cdd4b
Fast-forward
 README.md | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 README.md

Lets check our status again to confirm we are up to date:

git status
On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

There! Your local git is up to date, and you can start working on your project!

Git Pull

But what if you just want to update your local repo, without going through all those steps?

pull is a combination of fetch and merge. It is used to pull all changes from a remote repository, into the branch you are working on.

Lets make another change to the Readme.md file on GitHub.

Use pull to update our local Git:

git pull origin
remote: Enumerating objects: 5, done.
remote: Counting objects: 100% (5/5), done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 1), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (3/3), 794 bytes | 1024 bytes/s, done.
From https://github.com/w3schools-test/hello-world
   a7cdd4b..ab6b4ed  main       -> origin/main
Updating a7cdd4b..ab6b4ed
Fast-forward
 README.md | 2 ++
 1 file changed, 2 insertions(+)

That is how you keep your local Git up to date from a remote repository. In the next chapter we will look closer at how pull and pull requests work on GitHub.