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About Eddu Melendez

Eddu Melendez
Eddu is a Peruvian software engineer. He is interested in Java, Spring Framework and Mule ESB. He is also very enthusiastic to learn new stuff.

Git “Hello World” Example

In this example we shall show you how to start with Git. Git is a Version Control System (VCS) like CVS or Subversion but with one big difference it is not central repository, it is distributed.

First, we shall install git. You can download the installer to any O.S. from git-scm site here. Also, we will need an GitHub account in order to complete some steps in these example.

Note: We should take into account that the latest version is not available for all O.S at the same time.

1. History

  • Started at 2005
  • Created by Linus Tolvards
  • Written in Perl and C

2. Advantages

  • Allow different topologies (centralized, hierarchical, distributed)
  • Backup are easy
  • Reliable branching/merging
  • Full local history

3. Git Protocols

  • HTTP/HTTPS
  • GIT
  • SSH
  • File

4. Example

Before to start with the example, we need to setup git after the installation. There are three configuration levels (system, global, local). For more information, visit Git Configuration Section.

git config --global user.name "[name]"
git config --global user.email "[email address]"
  1. Create hello-world directory and make your first git local repository.
    mkdir hello-world
    cd hello-world
    git init
    

    By default, master is the name of branch.

  2. Create a README.md file and add your first commit using git commit --message or git commit -m.
    echo "Lorem ipsum dolor sit amet, eros maiestatis ei mel, utroque accumsan no pri. Ne his vocent tractatos, an soluta mollis sea. Delicata persequeris ne mei, cum no commodo detracto. Eu eam habemus lucilius. Facer sonet lobortis id pri, delectus fabellas id cum. Cum ex iuvaret inermis conclusionemque." >> README.md
    git add README.md
    git commit -m "Initial commit"
    

    File status in git repositories:

    • Untracked, initial status for new files.
    • Staged, after git add execution.
    • Unmodified, once git commit command is performed.
    • Modified, files committed have been edited.
  3. Create a GitHub account and create your repository.
    Create GitHub Repository 1

    Create GitHub Repository 1

    Create GitHub Repository 2

    Create GitHub Repository 2

    Create GitHub Repository 3

    Create GitHub Repository 3

  4. At this time, all changes are in our local repository but before to push local changes to the remote repository we need to add the remote url in the local repository. The first command is git remote --verbose or git remote -v show us the list of remote repositories associated but in this case is empty. Second command is used to add remote repositories.
    git remote -v
    git remote add origin git@github.com:eddumelendez/hello-world.git
    

    After that, we can run git remote -v and we will see something like this:

    origin git@github.com:eddumelendez/hello-world.git (fetch)
    origin	git@github.com:eddumelendez/hello-world.git (push)
    
  5. Now, our local repository has communication with the remote repository. This allow us to push local changes to the remote repository on GitHub.
    git push origin master
    
  6. Let’s create a new branch named development and add CONTRIBUTION.md file.
    git branch development
    git checkout development
    echo "Contribution" >> CONTRIBUTION.md
    

    We can use just one command git checkout -b development instead git branch development and git checkout development.

    In order to see the list of branches we can use git branch -a, the result must be:

    * development
    master
    

    (*) means that we are working in that branch.

  7. Commit new file to the local repository in development branch.
    git add CONTRIBUTION.md
    git commit -m "Add CONTRIBUTION.md file"
    
  8. Let’s review the log. Our development branch must have one additional commit to master.
    git log --oneline
    

    Terminal will display:

    11251d9 Add CONTRIBUTION.md file
    a466c08 Initial commit
    
  9. In order to see the differences among our branches we will use git diff command
    git diff master.. development

    In the terminal, we can see that there are a new file with content text Contribution.

    diff --git a/CONTRIBUTION.d b/CONTRIBUTION.d
    new file mode 100644
    index 0000000..e07fa82
    --- /dev/null
    +++ b/CONTRIBUTION.d
    @@ -0,0 +1 @@
    +Contribution
    
  10. Finally, since we have been working in a different branch (development). We need to merge these changes in the main branch (master). Now, we will use git merge command.
    git checkout master
    git merge development
    

    Now, we will create another branch from master and will make changes to solve conflicts in merge.

  11. Create refactor branch from master.
    git checkout -b refactor
  12. Edit README.md file, we are going to change word utroque to refactor.
  13. Back to the master branch and edit README.md file, we are going to change word utroque to master.
    git checkout master
  14. Let see the difference among master and refactor
    git checkout refactor
    git diff master.. refactor
    

    The output is:

    diff --git a/README.md b/README.md
    index 642ff12..ba22bb0 100644
    --- a/README.md
    +++ b/README.md
    @@ -1 +1 @@
    -Lorem ipsum dolor sit amet, eros maiestatis ei mel, master accumsan no pri. Ne his vocent tractatos, an soluta mollis sea. Delicata persequeris ne mei, cum no commodo detracto. Eu eam habemus lucilius. Facer sonet lobortis id pri, delectus fabellas id cum. Cum ex iuvaret inermis conclusionemque.
    +Lorem ipsum dolor sit amet, eros maiestatis ei mel, refactor accumsan no pri. Ne his vocent tractatos, an soluta mollis sea. Delicata persequeris ne mei, cum no commodo detracto. Eu eam habemus lucilius. Facer sonet lobortis id pri, delectus fabellas id cum. Cum ex iuvaret inermis conclusionemque.
    

    As we can see, there are conflicts between README.md files. Now, we will solve these conflicts in our merge process.

    <<<<<<< HEAD Lorem ipsum dolor sit amet, eros maiestatis ei mel, master accumsan no pri. Ne his vocent tractatos, an soluta mollis sea. Delicata persequeris ne mei, cum no commodo detracto. Eu eam habemus lucilius. Facer sonet lobortis id pri, delectus fabellas id cum. Cum ex iuvaret inermis conclusionemque.
    ======= Lorem ipsum dolor sit amet, eros maiestatis ei mel, refactor accumsan no pri. Ne his vocent tractatos, an soluta mollis sea. Delicata persequeris ne mei, cum no commodo detracto. Eu eam habemus lucilius. Facer sonet lobortis id pri, delectus fabellas id cum. Cum ex iuvaret inermis conclusionemque. >>>>>>> refactor
    
  15. In order to proceed with merge. We need to locate at the branch we want to merge changes, in our case master is that branch. Now, we will perform git merge
    git checkout master
    git merge refactor

    Now, we are going to work  with the remote repository. You can clone the repository created on GitHub which was created in previous steps using git clone:

    git clone https://github.com/eddumelendez/hello-world.git hello-world-copy
    

    This working copy is out-of-date. But, imagine you have been working in a new feature in the master branch. There are two way to update. Using a rebase or merging changes.

4.1 Rebase

git pull --rebase origin master
git log --oneline

As you can see, your last commit is on the top. So, git pull --rebase have reallocated your commit. You can have some conflicts in the rebase process and there are three commands git rebase --continue, apply changes to the next commit,git rebase --skip, ignore the current commit and, git rebase --abort, abort all rebase process.

4.2 Merge

git fetch origin master
git merge origin/master

5. Resources

6. Download the source code

This was an example about Git “Hello World”.

Download
You can download the source code of this example here: Git_Hello_World.zip
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