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
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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
  • 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!
  • 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
A repository can have multiple remotes. Use git remote to list them all.

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 pull is actually two commands in one. It's the same thing as doing git fetch <branch> + git merge <branch>

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

.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
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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 " 📄" 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 "" to discard the changes made to the file (be careful!)

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?

In GitLab, the setting is under Manage > Members

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