1.9 Use Git for Version Control

 

Use Git for Version Control

Here, you will learn how to get started working with Git, one of the main tools when developing code. You will learn how to clone a repository, manage the local repository, and push the changes back to the remote. To understand how GUI-based Git software such as Git extension in Visual Studio Code works, you will be managing the repository using the command-line commands.

Note

Click the Initialize button to start the lab. A progress bar will show you when the lab is initialized and active. Please be patient with the initialization process; several components are loading and getting ready.

After the initialization is complete, start the lab within 10 minutes, or it will be automatically terminated. After you have entered the active lab, do not navigate away from the lab page until you have completed that lab exercise, or it will be terminated.

Note

In case you encounter issues with writing code during the lab, please find the final code snippets in the /home/lab_solutions directory.

Open Transcript

You are using a US English keyboard layout. This cannot be changed once the lab has initialized.

 Visit Device Help for info about changing the OS keyboard layout and screen resolution after lab initialization.

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You may navigate away from this page once you begin initializing the lab.

You will be notified once the devices are ready.

Clone Git Repository

In this procedure, you will access the GitLab site available in the lab environment, log in to the site, and obtain the link for cloning an existing repository to your local working environment.

Step 1

From the Student Workstation, open the Firefox browser and go to http://dev.gitlab.local. Sign in with the username student and password 1234QWer; ignore the message about the connection not being secure.

Answer

Step 2

You will be on the Projects page, where you will see an already created project named devnet-lab02. You will clone this repository to your lab workstation machine.

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Step 3

From the taskbar, open the terminal, or open Visual Studio Code and use its terminal.

Step 4

Move to your working directory, /home/student/working_directory.

Answer

student@student-workstation:~$ cd /home/student/working_directory
student@student-workstation:~/working_directory$

Step 5

Configure the Git username and email. Git will use these credentials when you publish changes to the remote repository.

Answer

student@student-workstation:~/working_directory$ git config --global user.name "student"
student@student-workstation:~/working_directory$ git config --global user.email student@dev.local
student@student-workstation:~/working_directory$

Step 6

On the GitLab Projects site click on devnet-lab02 project to get to the project for devnet-lab02. Copy the link for cloning the repository by clicking Clone in the top right and then clicking the copy icon next to the HTTP URL. The URL will be copied in your clipboard. Dismiss the banners on top of the page.

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Step 7

In the terminal, using the copied URL, clone the repository from GitLab into the current directory (using the "." as the current directory) so that you will be able to work with files in the repository. Enter the username student and the password 1234QWer, the same credentials used when you logged in to the GitLab site.

Answer

student@student-workstation:~/working_directory$ git clone http://dev.gitlab.local/student/devnet-lab02.git .
Cloning into '.'...
Username for 'http://dev.gitlab.local': student
Password for 'http://student@dev.gitlab.local': 1234QWer
remote: Enumerating objects: 3, done.
remote: Counting objects: 100% (3/3), done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.

Note

The dot at the end of the git clone command defines the path to where the repository is cloned. If you omit the dot, a new directory is created that contains the repository.

Step 8

List the contents of the cloned repository. You can see the same README.md file as on the remote repository now downloaded locally. There is also the .git file where everything that Git needs for keeping track of your project will be stored.

Answer

student@student-workstation:~/working_directory$ ls -la
total 16
drwxr-xr-x  3 student student 4096 Sep 23 05:56 .
drwxr-xr-x 29 student student 4096 Sep 23 05:17 ..
drwxrwxr-x  8 student student 4096 Sep 23 05:56 .git
-rw-rw-r--  1 student student   36 Sep 23 05:56 README.md

Commit and Push Changes

In this procedure, you will learn how to verify the status of the local repository, how to add files, commit them, and finally push them to the remote repository—all from the terminal and using the Git extension in Visual Studio Code.

Step 9

In the working directory, create a file called lab02.py using touch.

Answer

student@student-workstation:~/working_directory$ touch lab02.py

Step 10

Run the git status command to check the current state of the repository.

Answer

student@student-workstation:~/working_directory$ git status
On branch master
Your branch is up to date with 'origin/master'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        lab02.py

nothing added to commit but untracked files present (use "git add" to track)
student@student-workstation:~/working_directory$

Step 11

To add the lab02.py file to the repository, you first need to start tracking it. Run the git add lab02.py command.

Answer

student@student-workstation:~/working_directory$ git add lab02.py

Step 12

Run the git status command. The command reveals that the file is now staged and will be included in the next commit.

Answer

student@student-workstation:~/working_directory$ git status
On branch master
Your branch is up to date with 'origin/master'.

Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        new file:   lab02.py

student@student-workstation:~/working_directory$

Step 13

Commit the file to your local repository. The commit message has to describe what is included in this commit. Run the git status command afterward, and you will see that the local copy of the master branch is ahead of origin/master on the GitLab server for one commit. This means that the lab02.py file is currently part of your local repository but not yet on the GitLab remote server.

Answer

student@student-workstation:~/working_directory$ git commit -m "Add lab02.py file"
[master 126171c] Add lab02.py file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 lab02.py
student@student-vm:~/working_directory$ git status
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
student@student-vm:~/working_directory$

Step 14

To publish the commit, use the git push origin master command. Your local master branch will now be synchronized with the remote branch. Use the git status command to confirm that you are back to a clean working directory.

Answer

student@student-workstation:~/working_directory$ git push origin master
Username for 'http://dev.gitlab.local': student
Password for 'http://student@dev.gitlab.local': 1234QWer
Counting objects: 3, done.
Delta compression using up to 4 threads.
Compressingobjects: 100% (2/2), done.
Writing objects: 100% (3/3), 271 bytes | 271.00 KiB/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To http://dev.gitlab.local/student/devnet-lab02.git
   1c0ddd7..126171c  master -> master
student@student-workstation:~/working_directory$ git status
On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

Note

For simplicity reasons, the master branch is not a protected branch in this repository. When developing the code in a team, the master branch might be a protected branch.

Step 15

Refresh the GitLab devnet-lab02 project page in your Firefox browser. You will see that there was a new commit done by student and that the lab02.py is now part of the repository.

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Step 16

Click the Add lab02.py file commit message. You will see which changes to the repository files were done in this commit.

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Step 17

From the desktop, open Visual Studio Code, and then Click Open folder... in the Start section on the Welcome page. Click Home and open working_directory. In the top-right corner, click OK.

Step 18

Open the lab02.py file, add a print statement, and save the file.

Answer

print('Working with Git')

Step 19

Once saved, in Explorer, the lab02.py file name changes color and an "M" is displayed next to it. It means the file has been modified; these changes are tracked by the Git extension in Visual Studio Code.

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Step 20

Click the Git extension icon in the activity bar to open it.

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Step 21

To commit the changes, enter Add print statement to lab02.py in the box, and then click the Commit symbol above the box.

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Step 22

Click Always to always stage the commits.

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Step 23

Now, you have committed the changes, and the local repository is ahead of the remote repository. To push the changes to the remote repository, click the three dots and click Push to....

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Step 24

You will be asked on which branch to push to; select the only one, and Visual Studio Code will push the changes to the remote repository. For the username and password, use student and 1234QWer.

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Note

If a pop-up window shows up in the bottom-right corner window asking you for permission to periodically fetch the code from the remote, click No to close it. You will be pulling the code manually in the next steps.

Step 25

Refresh the GitLab devnet-lab02 project page in your Firefox browser. You will see that there was a new commit done by the user student and that lab02.py was changed.

Answer

Compare Branches

In this procedure, you will learn how to create a branch, move between different branches, and how to compare them, finding the differences in the files.

Step 26

In the terminal, create a new branch on your local repository called staging and switch to it.

Answer

student@student-workstation:~/working_directory$ git checkout -b staging
Switched to a new branch 'staging'

Step 27

Back in Visual Studio Code add another print statement to lab02.py and save the file.

Answer

print('New branch')

Step 28

Compare the two branches using the git diff master command in the terminal. The current branch (staging) has two additional lines compared with the master branch.

Answer

student@student-workstation:~/working_directory$ git diff master
diff --git a/lab02.py b/lab02.py
index a82951a..1904e55 100644
--- a/lab02.py
+++ b/lab02.py
@@ -1 +1,3 @@
-print('Working with Git')
\ No newline at end of file
+print('Working with Git')
+
+print('New branch')
\ No newline at end of file

Step 29

Add the file to start tracking it, and commit the changes.

Answer

student@student-workstation:~/working_directory$ git add lab02.py
student@student-workstation:~/working_directory$ git commit -m "Add print statement"
[staging 8a5f68a] Add print statement
 1 file changed, 3 insertions(+), 1 deletion(-)

Merge Branch

Merging branches is a common task when working with Git. You will list the existing branches, check on which you are currently working on, and merge to the master branch without conflicts.

Step 30

To check the available branches, enter the git branch command in the terminal. The star will indicate the current branch.

Answer

student@student-workstation:~/working_directory$ git branch
  master
* staging

Step 31

Before merging the staging branch into the master branch, first switch to the master branch using the git checkout master command.

Answer

student@student-workstation:~/working_directory$ git checkout master
Switched to branch 'master'
Your branch is up to date with 'origin/master'.
student@student-workstation:~/working_directory$

Step 32

To merge the staging branch into the master branch, use the git merge staging command.

Answer

student@student-workstation:~/working_directory$ git merge staging
Updating 68391bd..8a5f68a
Fast-forward
 lab02.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Step 33

Verify the status of the local repository and push the changes to the remote branch. Enter the username student and password 1234QWer.

Answer

student@student-workstation:~/working_directory$ git status
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
student@student-workstation:~/working_directory$ git push origin  master
Username for 'http://dev.gitlab.local': student
Password for 'http://student@dev.gitlab.local':
Counting objects: 3, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 316 bytes | 316.00 KiB/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To http://dev.gitlab.local/student/devnet-lab02.git
   68391bd..8a5f68a  master -> master