Note: This lab is newly revised to work with VSCode rather than Eclipse. Expect some infelicities.
Note: In this lab, you will be configuring your account. The partner who is not logged in will likely have to repeat this work. Ideally, we’ll have a bit of time for that at the end of class.
a. Make sure you’ve read the Introduction to Git reading.
b. Make sure that you’ve done the Introduction to VSCode lab.
c. Log in and open a terminal window.
d. Create a directory to use for this lab. I’d suggest something like
~/CSC207/Git.
e. Open VSCode.
If you haven’t already done so, create a GitHub account at https://github.com/
a. Create an ssh keypair following the instructions at https://mathlan.sites.grinnell.edu/ssh/fastx/2019/07/22/Public-Private-Key-Pair/
b. Import the key to GitHub following the instructions at https://docs.github.com/en/authentication/connecting-to-github-with-ssh/adding-a-new-ssh-key-to-your-github-account
As you may recall, your life is easier if you do a bit of configuration before working with Git and GitHub. If you haven’t already done so, configure your account (name, email, editor).
git config --global user.name YOUR_NAMEgit config --global user.email USERNAME@grinnell.eduemacs, vim (or vim.basic), or even gedit or geany.
git config --global core.editor EDITORa. Log in to your GitHub account.
b. Somewhere on the page (along the left-hand column, at the time of this writing, but it changes), there should be a button labeled “Create Repository” (although that name changes, too). Click that button. A dialog should appear.
c. Name your repository (e.g., csc207-git-exercise).
d. Click the buttons to make it public.
e. Do not initialize the repository with a README file. Do not add a .gitignore file. Do not add a license. We basically want an empty repository.
f. Click “Create repository”.
a. In VSCode, open the command prompt with Ctrl-Shift-P.
b. At the prompt, enter/select “Java: Create Java Project…”. (Have you figured out what the ellipses stand for yet?)
c. When prompted for your build tool, select “No build tools”.
d. When prompted for a directory, use the directory you created in the preparation. It should be something like ~/CSC207/Git.
e. Enter a name for your project. You will generally want it to match the name you chose for your respository. In this case, it should be something like csc207-git-exercise. Hit return after entering the name.
f. In terminal, verify that the new directory was created.
a. In terminal, cd to that new directory. For example,
$ cd ~/CSC207/Git/csc207-git-exercise
b. Type git init. That command initializes the directory as a Git repository.
c. Type git status. That command will tell you the status of all the files. Since you haven’t added any files, it should say that the current directory is untracked.
d. Type git add README.md. That command will add only the README.md file to the repository.
e. Type git status again. Now, you should see that you have one file ready to be committed and two untracked directories.
f. Type git add .vscode src to add those two directories.
g. Type git status once more. You should see that three files are now ready to be committed.
h. Type git commit -m "Initial commit". That command commits the three files.
i. Type git branch -M main. That command indicates that we’re working on the main branch. (We’ll explore branches later.)
j. Type git remote add origin git@github.com:USERNAME/REPONAME.git, substituting your own GitHub username and the name of the repo you chose earlier. This command links your directory to your repository.
k. Type git push -u origin main. This should send the files to GitHub. When things go wrong, grab a mentor.
l. Check on GitHub to see if the files have been added.
In the VSCode lab, you created a simple “Hello World” Java program. Create a similar program in your new repository.
a. Create a new class, such as HelloWorld.
b. Add a main method to the class that has the following form.
public static void main (String[] args) {
PrintWriter pen = new PrintWriter(System.out, true);
pen.println ("Hello, GitHub!");
pen.flush();
} // main(String[])
c. Run your program to make sure that it works as you’d expect.
d. Save your program.
a. You’ve updated the repository and so should commit the code to the repository. You should also push it back to the main repository. So do so now. (That is, use the sequence of status, add, commit, and push to get the Java files into the GitHub repository.) (Note that we usually don’t push immediately immediately after each commit, but it’s handy to do so now. Normally, we do a series of small commits and only push once we’ve reached a larger goal.)
b. Go to GitHub and see if the changes you have made are visible. You may need to navigate a few layers deep, since VSCode makes a directory for each portion of the package.
a. Although we normally update code in our local copy of the repository, it is also possible to update code directly on GitHub. Navigate to the Java code you just wrote and click the “Edit” button.
b. Change the output. Then scroll to the bottom of the page, enter a commit message, and click “Commit”.
a. Our primary repository is now updated. How about our local repository? Let’s see. Switch back to the terminal window. Look at the file in the finder using less.
b. It is unlikely that the Java code changed. Why? Because you haven’t told Git to pull the updated version. Do so now.
c. Once you’ve issued the git pull command, verify that the file has indeed been updated in your local copy of the repository.
d. Finally, use git log to see a list of changes that have been made.
a. Switch back to VSCode.
b. Open the Java code you created and edited. Has it changed?
c. Your are likely to see a message from VSCode that your code is now out of synch, along with instructions for synching. Follow them.
a. In VSCode, change the output of your program slightly (i.e., change one of the strings).
b. Save the file.
c. In the terminal, type git status to determine whether or not Git saw the change. (It should note that your file has been changed.)
d. Type git diff to see what the change was. You should see your new code prefixed by plus signs, old code by minus signs, and a bit of context.
e. Commit your change, but don’t push it.
You have a local change that has not been pushed. Let’s see what happens if someone else also makes a change.
a. On GitHub, update the Java file by adding another print statement.
b. Determine what happens when you try to pull the updated version.
If all goes as expected, you should get a message like the following:
Auto-merging *FILE*
CONFLICT (content): Merge conflict in *FILE*
Automatic merge failed; fix conflicts and then commit the result.
c. Open the file in VSCode. You are likely to see lines that look something like this
<<<<<<< HEAD
*CODE*
=======
*OTHER CODE*
>>>>>>> 68f7b764bb0e83971245e8db7e58c330c9d9d25c
d. These lines show the conflict. Fix the conflict and save the file.
e. Back in the terminal, add and commit the changed file. Then try pulling again. Git should now be happy.
The lab writeup on Gradescope asks a few questions about this lab and the VSCode lab. Answer those quesitons.
If you are working with a partner, your partner should configure VSCode and Git too. (They should create an account and set appropriate characteristics in the terminal.)
You did this lab using HTTPS connections to GitHub. HTTPS connections are easy and straightforward. However, they also require you to type a password each time you push code back to GitHub.
GitHub also permits you to create a pair of private and public RSA keys and to use SSH connections with those keys. In that case, you may have to type the passphrase you associated with your keys, but you won’t have to enter your GitHub account info.
Figure out how to set up an SSH connection with GitHub.
You’ll need to do this exercise with a partner.
First, figure out how to give someone else administrative access to your repository.
Next, verify that they have administrative access by having them make a change and upload it to the repository.
Finally, figure out what happens if the two of you make changes.
git config --global user.name YOUR_NAME
git config --global user.email YOUR_EMAIL
git config --global core.editor EDITOR
git help
git clone
git add
git commit
git pull
git push