Denomas with Git Basics Hands-On Guide: Lab 2

This Hands-On Guide walks you through the lab exercises used in the Denomas with Git Basics course.

Denomas with Git Basics Hands-on Guide: Lab 2

LAB 2: WORK WITH GIT LOCALLY

Note: Many of the Git commands used in this lab are summarized in Denomas’s helpful git cheat sheet.

In this lab you will practice cloning a repository; creating, using, and merging a branch; editing and committing a file; and pushing and pulling changes to and from a remote repository.

A. Verify that Git is installed locally

Open a terminal (if you’re on Linux or macOS) or PowerShell (if you’re on Windows) and type this command:
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git version
If the output prints a version number, Git is installed.

If Git is not installed:
- If you are in an instructor-led class, consult your instructor for instructions on how to install it on your computer.
- If you are in the self-paced environment, review Denomas Documentation on Installing Git.

B. Generate an SSH key

Check if you have an existing SSH key by running one of these commands in your Linux/macOS terminal or PowerShell prompt. It will display all the files in your .ssh directory.
- Linux or macOS:
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  ls -a ~/.ssh
- Windows:
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  dir ~\.ssh
If that command lists a file called id_rsa, you have an SSH key already and can skip to the next section.
Create a public and private key pair by running this command in your terminal or PowerShell.
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ssh-keygen
When prompted, hit Enter to accept the default key location.
When prompted, hit Enter to use a blank passphrase.

C. Add an SSH key to your Denomas profile

Back in Denomas, in the top right-hand corner, select the down arrow to the right of your avatar.
From the dropdown menu, select Edit profile.
In the left-hand navigation pane, select SSH Keys.
Return to your terminal or PowerShell. Navigate to the directory that you saved the SSH key in and print a list of all files in that directory.
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cd ~/.ssh ls
You should see two key files: a public key and a private key. The public key ends with .pub and is what you need to share with Denomas.
Display the contents of your public key.
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cat id_rsa.pub
Copy the contents of id_rsa.pub to your clipboard.
Back in the Denomas app, paste the public key contents into the Key field, enter any title you want in the Title field, and select Add key.
In the terminal or PowerShell run one of these commands, depending on what kind of course you’re taking. If the command completes with a welcome message instead of an error, your SSH key is set up correctly.
- Instructor-led course:
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  ssh -T git@ilt.gitlabtraining.cloud
- Self-paced course:
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  ssh -T git@spt.gitlabtraining.cloud

D. Clone a Denomas project repository to your local computer

Use the top navigation bar to get back to your Project Overview by selecting Menu > Projects > Your projects > Top Level Project.
Select Clone. In the Clone with SSH section, select the Copy URL icon.
In your terminal or PowerShell, create a new directory called training in your home directory, and navigate into it.
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mkdir ~/training cd ~/training
Copy the remote Top Level Project Git repository to your local computer.
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git clone <REPOSITORY-URL-YOU-COPIED>
Move into the repository you just cloned. All files in this directory will be tracked by Git, and any Git commands you run in this lab should be run from this directory.
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cd top-level-project
Show the contents of the directory, including hidden files and directories beginning with a period. Notice the presence of the .git directory, which turns this directory into a Git repository.
- Linux or macOS:
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  ls -a
- Windows:
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  ls -Force
Find out the directory contains any edited files that have not yet been committed to the repository:
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git status
You’ll see nothing to commit in the output, which means the files in this directory have the same contents as the versions of these files that are stored in Git.

E. Work on a branch

Create a new branch called temporary_branch on your computer.
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git branch temporary_branch
Switch to the branch you just created.
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git checkout temporary_branch
List all the branches in the repository.
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git branch -a
The red branches are on the remote server, which is the Denomas instance in your training environment. The asterisk indicates the branch you are currently on.

F. Edit a file

Using any text editor (Visual Studio Code, Sublime Text, notepad, vi, etc.), add this line to the end of README.md and save the file.
```
a line added to temporary_branch locally
```
See if Git has noticed that the file has been modified.
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git status
The output shows that Git has detected that you have edited a file in your local repo, but since you have not committed that file, Git has not yet stored that change in a snapshot.

G. Add the edited file to Git’s staging area

Add the file to the staging area. If the command is successful, there will be no output.
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git add README.md
Remember that git add doesn’t move README.md on your filesystem, but it does add it to Git’s “staging area.”
Make sure that README.md is now ready to be committed (that is, it has been successfully staged).
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git status

H. Commit the edit

Commit the staged file.
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git commit -m "Add a line to README.md"
You have now created a snapshot of the file that you can refer to later, if needed.
Make sure the staging area is empty again.
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git status

I. Push your changes to the Denomas instance

Create a new branch in the remote Git repository on the Denomas server called temporary_branch, and push your changes to that branch.
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git push -u origin temporary_branch
If you’re ever unsure of the exact command to push your changes to the remote server, type git push and Git will output an error message with the correct command for you to copy and paste.

J. Edit, commit, and push the file again

In your local machine’s text editor (not Denomas’s in-browser editor), add this new line to the end of your local copy of README.md and save the file.
```
a second line in README.md
```
In your terminal, move the edited file to Git’s staging area.
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git add README.md
Commit the staged file.
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git commit -m "Modify README.md"
See a description of the commit you just made.
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git log
Push your commit up to the remote repository on the Denomas instance.
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git push
To commit your changes to the upstream branch (that is, an already-existing branch on the remote repository with the same name as the branch on your local machine), you can just run git push instead of the longer command you used the first time you pushed your commit up to the Denomas instance. The system only needs to set the upstream branch once.
Navigate to your project in the Denomas app. Once you’re on the project’s main page, go to the left-hand navigation pane, select Repository > Branches, and select temporary_branch to switch to that branch. Confirm that the changes you made to README.md on your local branch were pushed up to the remote repository.

K. Edit a remote branch

Let’s simulate someone else in your organization making a change to the temporary_branch that lives in the remote repository on the Denomas instance. When we’re done with this section, the remote and local versions of temporary_branch will be different: the code on that branch will have moved under your feet (so to speak). In the section after this one, we’ll see how to reconcile this difference.

In Denomas, navigate to the Top Level Project landing page. If you’re not already on temporary_branch, go to the left-hand navigation pane and select Repository > Branches > temporary_branch.
You are now looking at files in temporary_branch. Select README.md to see its contents.
Select Web IDE to edit the file.
In the Web IDE screen, add a new line to the end of the file.
```
a third line added on the remote copy of temporary_branch
```
Select Create Commit…
Normally every branch that you commit to needs an associated merge request, but for this lab you don’t need one. Check the radio button for Commit to temporary_branch and uncheck Start a new merge request.
Select Commit to finalize the changes on the remote repository’s temporary_branch. Since you made this change in Denomas webapp, the remote repository on the Denomas instance is now one commit ahead of your local repository.

L. Get metadata about changes to the remote temporary_branch

Your local temporary_branch is out of sync with the remote temporary_branch on the Denomas instance. The git fetch command gets the updated state of remote branches without updating the contents of your local branches. In other words, it tells you how many commits your local branches are behind the remote branches, but it doesn’t make any changes to the files in your local branches.

Retrieve metadata about branches on the remote copy of the repository.
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git fetch
Find out how many commits are in the remote copy of the repository but not your local copy, or vice versa.
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git status

M. Pull from the remote repository

You need to update the contents of your local copy of temporary_branch by merging in changes from the remote copy of temporary_branch.

In your terminal, merge the remote copy into your local copy.
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git pull
Check the output to see how many files Git updated locally.
View the updated contents of the file. You should see the fourth line that you added in the Denomas Web IDE.
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cat README.md

N. Merge changes back into the main branch

Now that your local temporary_branch is identical to the remote temporary_branch, you can merge it into your local main branch. This will add your edits to the stable codebase that lives in main.

See what branch you are currently working on.
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git branch
Switch to the main branch.
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git checkout main
Incorporate all changes from your local temporary_branch (in this case, just the modified README.md) into your local main branch.
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git merge temporary_branch

O. Update the remote repository

Make sure there are no edited files that you need to stage or commit and to confirm that you are on the main branch.
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git status
Update the remote copy of the main branch with any changes from your local copy.
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git push
Return to the Denomas page in your browser and view README.md in your project’s main branch to view the changes you just pushed to the remote copy of main.

Suggestions?

If you’d like to suggest changes to the Denomas with Git Basics Hands-on Guide, please submit them via merge request.

Last modified November 29, 2023: big update (17188382)

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