GitHub

From Coder Merlin
Within these castle walls be forged Mavens of Computer Science ...
— Merlin, The Coder


GitHub Zombie Octocat

Curriculum[edit]

ExercisesIcon.png
 Coder Merlin™  Computer Science Curriculum Data

Unit: Lab basics

Experience Name: GitHub (W1007.10)

Knowledge and skills:

  • §10.231 Demonstrate proficiency in using a source control system for single-users
  • §10.232 Demonstrate proficiency in using a source control system with multiple users

Topic areas: Source control systems

Classroom time (average): 60 minutes

Study time (average): 180 minutes

Successful completion requires knowledge: understand the purpose of a source control system when working with multiple users

Successful completion requires skills: ability to push and pull changes to/from the source control system; ability to use a source control system to merge changes; ability to properly handle merge conflicts

Introduction[edit]

While using git locally is a wonderful way to track our revisions and enable us to rollback to previous versions, to take full advantage of git we'll use GitHub. GitHub is a service where we can replicate (copy) our repository and collaborate with others.

A GitHub Account[edit]

Your guide will set up a repository for your use for this assignment. Be sure to follow the instructions carefully. To participate, you'll need a GitHub account. GitHub accounts are free to create.

  1. Go to https://github.com
  2. Click the GitHub-Sign up Button.png button at the top, right-hand side of the page
  3. On the next page ("Set up your account"), there is a short form:
    1. Create a unique (and appropriate) username
    2. Provide an accessible email address, as directed by your guide
    3. Provide a password
    4. You might receive a small puzzle to solve; if so, solve the puzzle
    5. Click the "Create Account" button GitHub-Create Account Button.png
  4. On the next page you might have a brief survey. At the bottom, click the "Complete Setup" button GitHub-Complete Setup.png
  5. You'll receive an email to the address you specified.
    1. Check your email client and find the email from GitHub
    2. Click the GitHub-Confirm Email Button.png button

Configuration[edit]

To squelch the warning that occurs while pushing, execute:

jane-williams@codermerlin:~$ git config --global push.default matching

Note: This command, if successful, completes silently.

Token Allocation[edit]

As a safer alternative to passwords, tokens are:

  1. Unique to a service and therefore can't be reused on another
  2. Revocable individually without adversely affecting other credentials
  3. Limited to authorization for a specific use case without the need for broader access
  4. Random and thus not subject to dictionary attacks

To allocate your token for  Coder Merlin™  on GitHub carefully follow these instructions:

Generate a New SSH Key[edit]

jane-williams@codermerlin:~$  ssh-keygen -t ed25519 -C "jane-williams@codermerlin.com"

Be sure to replace the above email address with your actual email address used for GitHub.

You'll then be presented with a series of prompts. Unless otherwise instructed by your guide, press Return for each to accept the default.

Generating public/private ed25519 key pair.
Enter file in which to save the key (/home/jane-williams/.ssh/id_ed25519): Return
Enter passphrase (empty for no passphrase): Return
Enter same passphrase again: Return
Your identification has been saved in /home/jane-williams/.ssh/id_ed25519
Your public key has been saved in /home/jane-williams/.ssh/id_ed25519.pub
The key fingerprint is:
SHA256:t0kJmRZa4ImzPbO88e2Onkbuwbews73rzjSB5zifU9o john-williams@codermerlin.com
The key's randomart image is:
+--[ED25519 256]--+
+----[SHA256]-----+

Add the Key to GitHub[edit]

jane-williams@codermerlin:~$  cat ~/.ssh/id_ed25519.pub

Copy the contents of the file to your clipboard. Then:

  1. Go to GitHub.com
  2. In the upper-right corner of any page, click your profile photo, then click Settings.
  3. In the "Access" section of the sidebar, click SSH and GPG keys.
  4. Click New SSH key or Add SSH key.
  5. In the Title field, add a descriptive label for the new key.
  6. Paste your key into the Key field.
  7. Click Add SSH key.

Test your Key[edit]

jane-williams@codermerlin:~$  ssh -T git@github.com

If successful, you should see something similar to:

> Hi username! You've successfully authenticated, but GitHub does not
> provide shell access.

Assignments[edit]

Your guide will create a GitHub assignment for you. You'll receive an email with an invitation link.

  1. BEFORE clicking the link, sign in to GitHub using the correct account.
  2. Click the link.


Hint.pngHelpful Hint

Your guide will create assignments for you which are "Private"; they'll be visible only to you (or your group for group assignments) and your guide. If you create any repositories on your own, be sure you select the correct setting.

Joining the Classroom Roster[edit]

The first time you click an assignment, you'll be asked to join the classroom roster. You'll see a message similar to: "Join the classroom roster: Your teacher has configured this classroom to pair GitHub accounts with identifiers."

  1. Click your identifier. (Do NOT skip this step.)
  2. The next page presents you with an GitHub-Acccept This Assignment Button.png. Click the button.
  3. You might see a progress bar (or two). Be patient as your assignment is prepared. When the assignment is ready, you'll see the message: "You are ready to go!"
  4. A link should be ready at the very bottom of the page, immediately after the text "Your assignment has been created here:" Click that link. You'll need this link in a subsequent step in this experience.


Hint.pngHelpful Hint
The link that you just clicked is the link to your personal repository for the assignment. It might be something that you'd like to bookmark.

First GitHub Assignment[edit]

Your first GitHub assignment will be to sync all of your journals with GitHub. To do so, you'll need to specify a GitHub URL as your "remote" for your existing git repository.

Enter your Journals directory:

john-williams@codermerlin:~$ cd ~/Journals

Remember that you've already added all these files to your local git repository. You can easily verify this by checking the status.

john-williams@codermerlin:~/Journals$ git status

You should see something similar to:

On branch master

nothing to commit, working tree clean

Let's add the remote. To do so, we'll need the URL from the above assignment. It will be something similar to:
https://github.com/.../2024-journals-JohnWilliams
Be sure to use your own url, which will be unique to you.

john-williams@codermerlin:~/Journals$ git remote add origin https://github.com/.../2020-journals-JohnWilliams.git

Then, we can push our local commits to the remote server:

john-williams@codermerlin:~/Journals$ git push -u origin master

You'll then be promoted to enter your username and password. Remember to use your GitHub username and token. After the push is completed, go back to the browser and refresh the page.

Workflow Overview[edit]

Git-Workflow-Basic.png

The workflow when using a remote repository is very similar to that using only a local repository, with the exception of push and pull.

  1. add the files to the staging area
  2. commit the files to the repository
  3. push the local repository to the remote

The most significant difference is that we'll need to keep in mind that others might also be working on the remote repository, so we'll need to sync their remote changes with our local repository. The best practice is to perform a pull before beginning work in the working directory.

Tagging[edit]

As you progress through your work, whether it be code or prose, you'll accumulate more and more commits, each with its own version of a file. There will be times when you'll need to mark a specific commit. For example, you might want that commit to be reviewed by your editor or by quality assurance personnel. Git is able to mark specific points in the repository as being important. This process is called tagging, and the mark itself is called a tag. It's important to note that the entire repository at a given point in time is tagged, not one file or group of files.

Tagging Locally[edit]

A tag can be placed on the repository with the following command, replacing tagName with the actual name of the tag.

john-williams@codermerlin:~$  git tag tagName

For example:

john-williams@codermerlin:~$  git tag E1399.Outline

Pushing a Specific Tag to a Remote[edit]

To push a tag to a remote repository, use the following command:

john-williams@codermerlin:~$  git push origin tagName

For example:

john-williams@codermerlin:~$  git push origin E1399.Outline


CautionWarnIcon.png

Pushing a tag includes all required objects for that tag, but does NOT include any other references. For example, it does not include your commits. Therefore, it is vital that you first push your commits by executing:

john-williams@codermerlin:~$  git push

and then push any desired tags.

Deleting a Tag Locally[edit]

You can delete a tag locally by using the following command, replacing tagName with the actual name of the tag.

john-williams@codermerlin:~$  git tag --delete tagName

Deleting a Tag from a Remote[edit]

You can delete a tag from a remote with the following command, replacing tagName with the actual name of the tag.

john-williams@codermerlin:~$  git push --delete origin tagName

Best Practices[edit]

ComingSoonIcon.png
Coming Soon
  • Include only essential files required to reproduce project (e.g., source files)
  • Avoid unnecessary files (e.g., compiled products and temporary files)
  • How to use .gitignore

Key Concepts[edit]

Key ConceptsKeyConceptsIcon.png
  • GitHub is a service where we can replicate (copy) our repository and collaborate with others
  • GitHub serves as a remote repository
  • The workflow when using a remote repository is very similar to that using only a local repository except that additional commands are required
    • push pushes the files from the local repository to the remote repository
    • pull pulls the files from the remote repository to the local repository (and working directory)
    • tag marks a specific commit as 'special'
    • push origin <tag> pushes the specified tag from the local repository to the remote repository

Exercises[edit]

ExercisesExercisesIcon.png
  • Push all of the journals in the Journals directory to GitHub and be sure to continue to push all new/modified journals as well. Note that this applies to essays and excursions as well.
  • Journals and essays should be stored in your "Journals" directory and pushed to your "Journals" repository.
  • Exercises and excursions should be stored in your "Experiences" directory and pushed to your "Experiences" repository.
  • Your final version of any exercise must be tagged as <ExerciseName>.Final. For example, for J1006, the file will be named J1006.txt (because it is a text file) and the final version should be tagged J1006.Final

References[edit]


Experience Metadata

Experience ID W1007.10
Unit Lab basics
Knowledge and skills §10.231
§10.232
Topic areas Source control systems
Classroom time 60 minutes
Study time 3 hours180 minutes <br />
Acquired knowledge understand the purpose of a source control system when working with multiple users
Acquired skill ability to push and pull changes to/from the source control system
ability to use a source control system to merge changes
ability to properly handle merge conflicts
Additional categories