Howto git

Guillaume Gay, CENTURI multi-engineering

Outline

Git as a single user

Getting started
Git as an archive
How to revert mistakes
Backing up to github

Github and Gitlab, multi-user collaboration

Branches and forks
pull requests
Issues and bug reports
introduction to Continuous Integration

git as a single user

Getting started

1. Install git

Linux: sudo apt install git
Mac OS X: git-scm.com/download/mac

or brew install git

Windows: git-scm.com/download/win

2. Install a GUI (optional)

Github Desktop (Win & Mac, open-source)
Git Kraken (Win, Mac& Linux, free but not OSS)

3. Configure your name and email

In a terminal (“git bash” on Windows)

git config --global user.name "Guillaume Gay"
git config --global user.email "guillaume.gay.1@univ-amu.fr"

4. Create your first project

Create a directory (called e.g. Documents/GitTuto)
in the terminal cd to that directory:

cd Documents/GitTuto

The directory is empty:

ls -la

Tell git to start tracking this dir

git init

Now the directory isn’t empty

ls -la
tree .git/

You can do this on an existing directory

The .git directory contains all git needs to track your project

!! .git might contain lots of small files
!! Delete .git → lose history
You can move the whole directory (with the .git subdir.)

`status`

To know what is going on at any time, type:

git status

git as an archive manager

`add`

Create a (text) file, e.g. README.md
Write “This is a git tutorial” in it.

git status

git add README.md

git status

Now git knows about your file

`commit`

git commit -am "My first commit"

The message is mendatory

git status

Git registered your file

`diff`

Edit README.md (add some text) and

git status

You can see there are untracked changes

git diff shows what changed.

git diff

git commit -am "My second commit"
git status

Your changes were registered (wash, rince, repeat)

`log`

log: what happened before now

git log

`.gitignore`

Create a file called tmp_file.txt

git status

Create a file called .gitignore and write tmp_* in it.

Only .gitignore is listed as untracked

It’s good to have a direct read of the state of your code (in your editor or terminal)

how to cancel and revert mistakes

There are two commands depending on your git freshness

older git ( before 2.23 )

git checkout README.md

newer git ( after 2.23 )

git restore README.md

Those undo changes made since latest commit

You can restore older versions of the file.

For exemple to restore a file at a certain commit, you can reference this commit by its hash:

git restore -s ae2fd12 README.md

You can find a commit’s hash with git log

There are plenty of more powerfull things you can do, but I don’t know / need them!

Backing up to github

Create an account
Manage SSH

git communicates with public / private keys. To make it easier, we register a key on our github account.

ssh-keygen # creates a key

On github, go to settings > SSH and GPG Keys > New SSH key

Copy the content of .ssh/id_rsa.pub there.

Local first

`remote add`

Create a new (empty) “GitTuto” repository on github
Copy the repo URL
Declare it as a remote

git remote add origin git@github.com/glyg/GitTuto.git

Change your principal branch from master to main

git branch -M main

`push`

Publish the local files to github

git push -u origin main

Make new changes, commit and push

git commit -am "changed README.md"
git push

`pull`

Make a change on README.md on github & commit there

git pull
git log

Distant first

`clone`

In another place on your computer (or on another computer):

git clone git@github.com/glyg/GitTuto.git
cd GitTuto

git status
git remote show origin

Summary

Branches and how to merge them (2nd session)

branches are cheap, use them!

Collaboration with Github and Gitlab

One user, several repositories

One user, several repositories

Two users, several repositories

Two users, several repositories

Two users, several repositories

Issues

Do not hesitate to report problems
Be polite etc.
Use issues to discuss and track your problems
What’s a minimal reproducible example?

A word on Continuous Integration

Automates tests
No more ‘but it works on my machine :/’
Can be tricky to setup

Questions, comments, suggestions:

github.com/centuri-engineering/git_tuto

Slack Channel:

centuri-livingsystems.org/multi-engineering-platform