Git

version control, for beginners

$ git init

Who has used Git before?

Who has used it in a team?

Who has ever lost work they wanted back?

Who has a folder called
`final-v2`?

The fear of Git

$ ls ~/projects

project/
project-revised/
project-final/
project-final-FINAL/
project-final-real/
project-final-real-2/

Version control

Snapshots of your code over time
Parallel work — many people, different parts, at once
Rewind — go back to any snapshot

Git is not the only one. It is just the winner:
CVS · Subversion · Mercurial · TFS · Perforce

Centralised vs distributed

Git vs. GitHub vs. GitLab

Branches and commits

A commit is a point. A branch is just a name pointing at one.

How Git works

git pull = git fetch + git merge

Demo

Getting started

Create a new repositorygit init

Clone an existing onegit clone <url>

Check statusgit status

Check the loggit log

Stage one filegit add <file>

Stage everythinggit add .

Commit what is stagedgit commit -m 'message'

Create a branchgit branch <branch-name>

Switch to a branchgit checkout <branch-name>

Both at oncegit checkout -b <branch-name>

Atomic commits

Use meaningful commit messages

$ git log --oneline

a1b2c3d  created main loop & timing control
4d5e6f7  enabled config file parsing
8a9b0c1  misc bugfixes
2d3e4f5  code additions/edits
6a7b8c9  more code
0d1e2f3  here have code
4a5b6c7  aaaaaaaa
8d9e0f1  adkfjslkdfjsdklfj
2a3b4c5  my hands are typing words

Write for the person reading this in six months.
It will probably be you, and you will not remember.

Conflict resolution

Merging two branches may cause a conflict
A conflict means Git could not choose for you — it is not an error, it is a question
You resolve it by editing, not by commands alone
Then add the file to mark it resolved, and commit to finish the merge

What a conflict looks like

<<<<<<< HEAD (current change)
    readFileAndGenerating(file, split);
=======
    readFileAndGenerate(input, split);
>>>>>>> main (incoming change)

    i18nFileGenerate(output, options || null);

Delete the markers. Keep the code you want — maybe both, maybe neither. VS Code puts buttons on top of exactly this.

Demo

Merging and conflicts

Merge a branch into this onegit merge <branch>

Back out of a failed mergegit merge --abort

Mark a file resolvedgit add <file>

Finish the mergegit commit

$ git merge --abort

Nothing is lost — you are back exactly where you were before the merge.

Undoing changes

First question: where is the change right now?

Reset vs revert

Reset what only you have. Revert what everyone has.

Demo

Undo commands

Throw away edits to a filegit restore <file>

Unstage a file, keep the editsgit restore --staged <file>

Fix the last commitgit commit --amend

Undo the last commit, keep the changesgit reset --soft HEAD~1

Undo a commit that is already pushedgit revert <commit>

Park your changes, get them back latergit stashgit stash pop

$ git reset --hard

The one undo you cannot undo: uncommitted changes are gone for good.

Thank you

Sign in

first time

$ git clone the address below

$ cd attendance

back again

$ cd attendance

$ git pull

then sign in

$ echo "Your Name" > your-name.txt

$ git add your-name.txt

$ git commit -m "your-name is here"

$ git push

Push rejected? Someone pushed first. Run git pull --rebase, then git push again.

0 signed in · connecting…

https://playground.hackenshaw.com/git/attendance.git

Workflow — solo dev

Switch to main and get latestgit checkout main

git
                            pull

Create a branch for your feature

git checkout -b
                            feature/add-login

Make changesgit add .

git commit -m "Add login
                            form"

Merge when donegit checkout main

git merge
                            feature/add-login

Clean upgit branch -d feature/add-login

Workflow — team, starting out

Switch to main and get latestgit checkout main

git
                            pull

Create a branch for your feature

git checkout -b
                            feature/add-login

Make changesgit add .

git commit -m "Add login
                            form"

Stay up to dategit fetch origin

git rebase
                            origin/main

Merge when donegit checkout main

git merge --ff-only
                            feature/add-login

git push

Clean upgit branch -d feature/add-login

Workflow — team, in practice

Switch to main and get latestgit checkout main

git
                            pull

Branch for your feature

git checkout -b
                            feature/add-login

Make changesgit add .

git commit -m "Add login
                            form"

Sync with the remote

git push origin
                            feature/add-login

Open a pull request

base branchmaincompare branchfeature/add-login
add title, description, context

Review & discuss

comment or suggest changes
testing
push fixes — they join the PR automatically

If main moved since you branchedgit fetch origin

git
                            merge origin/main

git push

Merge

Squash → one clean commit
Rebase → linear history
Normal merge → not recommended

Clean upgit branch -d feature/add-login

git push origin
                            --delete feature/add-login

Resources

notes.txt	today's handout — everything we covered, in one text file
learngitbranching.js.org	branches and merges, drawn as you type them
ohmygit.org	an actual game about learning Git
ohshitgit.com	how to undo the thing you just did
w3schools.com/git	a click-through tutorial from zero
git-scm.com/book	Pro Git — the reference, free online

And the one already on your machine: git help <command>.

Questions?

$ open

presentations.hackenshaw.com/downloads/git-intro-fontys.html

These slides, with a link to notes.txt.

$ thanks for coming

Git

Who has used Git before?

Who has used it in a team?

Who has ever lost work they wanted back?

Who has a folder calledfinal-v2?

The fear of Git

Version control

Centralised vs distributed

Git vs. GitHub vs. GitLab

Branches and commits

How Git works

Demo

Getting started

Atomic commits

Use meaningful commit messages

Conflict resolution

What a conflict looks like

Demo

Merging and conflicts

Undoing changes

Reset vs revert

Demo

Undo commands

Thank you

Sign in

Workflow — solo dev

Workflow — team, starting out

Workflow — team, in practice

Resources

Questions?

Feedback

Who has a folder called
`final-v2`?