programming-basics/1-git-basics.md

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Project management 1. Git basics	true	true	mathjax	buutti

Project management 1. Git basics

Basic Git workflow

• You have to tell everything you want to happen to Git explicitly by using Git commands
• A common Git workflow consists of these four steps:

1. Edit: You make changes in some code file
2. Stage: You tell Git what files you've changed (git add)
3. Commit: You tell Git what changes you made in that file (git commit)
4. Push: You upload those changes to a remote repository (git push)

Repositories

• Repository is essentially a place to store code files in
• Usually, we are dealing with two repositories: a local and a remote one
  • A local repository is the one on your computer
  • A remote repository is stored in a cloud service like GitHub
  • Here is the remote repository for the materials of this course
  • Changes are synced between these two repositories manually

git init

• Initialization needs to be done for every new Git repository
• There are two ways to initialize a repo:
  • a) Creating the local repository first:
    • Use git init to make your current folder a new Git repository
  • b) Creating the remote repository first / continuing an existing project:
    • Clone a remote repository into your computer (See: git clone)
• Note: Never initialize a Git repository in a cloud storage folder!

.git folder

• Initialization adds a hidden .git folder inside a directory
  • This is where Git stores all its repository data.
  • Do not touch it!
• The .git folder ONLY appears in the root directory of the repository
  • If you see the .git folder in any of the subdirectories of the repository, something has gone wrong!
  • You have initialized a repository inside repository

git status

• Using the command git status shows your current situation.
• If you're unsure what to do, it's never a bad idea to run git status

git add

• Uploading changes to GitHub from your local machine takes three steps (see Basic Git workflow from earlier)
• The first phase is staging with git add:
  • The command git add readme.md stages the file readme.md
  • After doing it, git status tells this:

    Changes to be committed:
      (use "git restore --staged <file>..." to unstage)
            modified:   readme.md
    

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• Basically, with git add file you tell Git that you want to do something with file.
• Note: If you just want to push all the changes you've made, you can use git add . to stage all the files in your current folder and its subfolders
  • Be careful! Only do this after checking what changes have been made with git status
• Note 2: Use git add <filename> -p if you only want to stage some lines from a file you've worked on.
• Note 3: The counterpart to git add is git rm, which removes previously added files from Git's perspective

git commit

• After you have staged all the files you want, the second step is to commit your changes
  • In the commit, you will explain what changes you've made
  • This message will be visible in GitHub
  • git commit -m "add new enemy"
• Every new commit creates a new point in the project timeline.
  • You can always jump back between different points (See git checkout)
• Commit message should clearly, concisely tell what kind of changes you have made

git push

• The third step is pushing the changes to GitHub
• The previously-made commit action is local
  • No changes have gone to the remote repository yet!
  • To upload changes to the remote repository, use git push
  • Then you're done!

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• Note: When pushing for the first time, Git might nag you:

  fatal: The current branch master has no upstream branch.
  To push the current branch and set the remote as upstream, use
  
      git push --set-upstream origin main
  

• You can just follow its orders (see the command on the third line!) and you're good to go
• Generally, when Git gives you a warning, error, or some other message, it's a good idea to read it and follow the orders.

git remote

• If you have initialized a Git repo already with git init, don't use git clone!
  • Instead, run git remote add origin <URL>
  • Here, the name origin refers to the remote repository
  • origin is just the default name for a remote: other names can be used instead!
• To check which remote repository the current local repository is linked to, use
  • git remote -v

Exercise 1a. Initializing a repo

• Initialize a new repository locally.
• Create a new file GitTest.md with some lines of text in it.
• Commit changes.
• Create a new empty repository on GitHub.
• Use git remote add origin <url> to connect your local repo to the GitHub repo.
• Push changes to GitHub. Go to GitHub and see that GitTest.md is there!

git pull

• git pull applies changes from the remote repository into the local repository
  • Counterpart to push
• Very common when working in a team
  • Note: During teamwork it's a good idea to always pull before pushing
• If you only work alone on a single computer, seldom needed

git clone

• Remote repositories have an URL address that can be used to download the code to your machine
  • The address can be found under the Clone button in the repository webpage
• Use the URL to download a remote repository:
  • Run git clone <URL>
  • Example: git clone https://github.com/borbware/unity-basics-course.git
  • Remember: this initializes the repo, so git init not needed.
• Simplest way to create a new, empty repository:
  • 1 - Initialize the repo in the Github/Gitlab/etc website
  • 2 - Clone the repo.

Exercise 1b. Cloning a repo

• Create a new repository on GitHub and clone it with HTTPS to your machine.
• Then, create a new file GitTest.md with some lines of text in it.
• Commit and push changes to GitHub.
• Go to GitHub and see that the file is there!

Extra: HTTPS vs SSH

• There are two ways to communicate with GitHub, HTTPS and SSH
• HTTPS: https://github.com/borbware/unity-basics-course.git
  • the easier way
  • you log in with your GitHub credentials that get stored in the Git Credential Manager
• SSH: git@github.com:borbware/unity-basics-course.git
  • Connecting to GitHub with SSH
  • You need to generate a computer-specific SSH key and add it to your GitHub settings

.gitignore

• Sometimes your project has local files that should NOT be uploaded to GitHub
  • List those files in a .gitignore file in your Git project folder
• You can create it by yourself and define file names or folders which Git will then ignore in the commits, e.g.,

    someScript.cs
    /folder
    *.html
  

• Note: If you add a file to .gitignore that was committed earlier, Git doesn't "forget" it automatically.
  • You can make Git forget it with git rm --cached filename

VS code: Source control

• The source control tab is very useful for managing your Git workflow
• Unstaged changes are shown under Changes
  • Press "+" to stage a file
• Staged files are shown under Staged changes
  • Press "-" to unstage a file
  • Press "\curvearrowright 📄" to open the file
• Click the filename to see what changes you've made in a side-by-side comparison view (see the next slide!)
• Press "\curvearrowleft" to discard the changes made to the file (be careful!)

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Exercise 2. Git collaboration

• Work on this exercise with your group.
• Choose someone's test repository from Exercise 1b to use in this exercise.
• While others clone the repo to their machine, the owner should add other group members as collaborators of the repo in the repository's settings on GitHub.
• Then, everyone should make changes to the markdown file in the repository!

What happens if you make changes to the same line simultaneously?

Troubleshooting: master vs. main

error: failed to push some refs to [your-url]

• Possible reason: GitHub has a main branch, while your local repository has master
• Fix: Run git branch -m main to rename your local master to main

Note about longer push and pull commands

• After initialization, why do I have to use longer push and pull commands?
  • Short answer: because we didn't clone the repo, but rather added the remote into an empty one with git remote add origin.
  • git pull origin main: After adding a remote, we don't yet know which branch to pull from. main (or master!) is the default branch
  • git push --set-upstream origin main: In the first push, we decide which branch to link our current branch into.
  • Afterwards, we can just use git push and git pull.

Reading

• Using version control in VS code