Introduction to Version Control With Git

Elsa Gonsiorowski

• HPC I/O Support Specialist in Livermore Computing since 2016
• Developer for SCR: Scalable Checkpoint Restart library
• LC Hotline tech
• Working remotely in RI
• Excited about emacs, org-mode, static websites, fish shell, cmake, documentation, crossfit, rowing, knitting

Schedule for the Week

Caveats

• This is a 1 hour session, there is so much more to learn!
• You can type along, but I will be moving fast
• Slides available on myconfluence.llnl.gov/display/CF

Raise Your Hand

• If you can find the "Raise Hand" button on Webex
• If you know someone else attending this lecture
• If you've played a video game with "checkpoints"
• If you've used "Track Changes" (MS Word or Google Docs)
• If you know you have git installed on your system

VC Through Naming

VC in Parallel

Key Features

• Version control allows you take checkpoints or snapshots as you work on a project
• Version control is unlimited undo (but not at a granular level)
• Version Control allows many people to work in parallel

Assumptions

• You are familiar with working on the command line

• You know the commands:

  ls	list files, with the flags -al
  cd	change directory
  mkdir	make directory
  echo	repeat text
  >	output redirection

Using These Slides

• Code and command examples are written in a fixed-width font: like this
• Commands that you should run in a terminal (or "on the command line") are shown with a leading $. Do not include the $ when actually trying to run the command

Configuring from the Command Line

$ git config --global user.name "Ada Lovelace"
$ git config --global user.email "ada@lovelace.io"
$ git config --global core.editor "emacs -nw"
$ git config --global init.defaultBranch main

Help with Config

$ git config --list
$ git config --help
$ cat ~/.gitconfig

File: ~/.gitconfig

[core]
    editor = emacs -nw
[init]
    defaultBranch = main
[user]
    name = Ada Lovelace
    email = ada@lovelace.io

Create a Repository

$ cd ~/Desktop
$ ls -al
$ mkdir Planets
$ cd Planets
$ git init
Initialized empty Git repository in /Users/gonsie/Desktop/Planets/.git/
$ ls -al
total        0
drwxr-xr-x   3  gonsiorowski1 59746  96 Jul 11 10:43 .
drwx------@ 16  gonsiorowski1 59746 512 Jul 11 10:43 ..
drwxr-xr-x   9  gonsiorowski1 59746 288 Jul 11 10:43 .git

Query Git

$ git status
On branch main

No commits yet

nothing to commit (create/copy files and use "git add" to track)

Add a File

$ echo "Cold and dry, but everything is my favorite color" > mars.txt
$ ls -al
total        0
drwxr-xr-x   3  gonsiorowski1 59746     96 Jul 11 10:43 .
drwx------@ 16  gonsiorowski1 59746    512 Jul 11 10:43 ..
drwxr-xr-x   9  gonsiorowski1 59746    288 Jul 11 10:43 .git
-rw-r--r--   1  gonsiorowski1 59746     50 Jul 11 11:08 mars.txt
$ git status
On branch main

No commits yet

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        mars.txt

nothing added to commit but untracked files present (use "git add" to track)

Start Tracking Your File

$ git add mars.txt
$ git status
On branch main

No commits yet

Changes to be committed:
  (use "git rm --cached <file>..." to unstage)
        new file:   mars.txt
$ git status --short
A  mars.txt

Commit Your Changes

$ git commit -m "started work on mars.txt"
[main (root-commit) 3383acd] started work on mars.txt
 1 file changed, 1 insertion(+)
 create mode 100644 mars.txt
$
$ git status
On branch main
nothing to commit, working tree clean

gonsie/thesis

gonsie/dotfiles

This is just the beginning

• More things to learn:
  • Explore history
  • Collaboration through "pull" or "merge" requests
  • Platforms: GitHub and GitLab

Git Caveats

• Git is powerful
• Git has a terrible user design
• Git is hard to fully learn by yourself
• Git (like any other tool) takes time and practice to get good

Get Social

• Sign up for GitHub
  • Follow your friends, star your favorite (LLNL) projects
  • If you follow me this week I will follow you back
• With permission: use GitHub to showcase projects
  • Get approval before posting LLNL code
  • Get permission before posting homework solutions

Git Lessons

• Git Cheetsheet
• Software Carpentry: Git Novice
• GitLab: Use Git Tutorials
• Atlassian (BitBucket): Learn Git

Advanced Git Resources

• GitHub Skills
• Learn Git Branching Interactively
• Choose your own adventure: undoing, fixing, or removing commits in git

Tools

Created with Emacs, Org Mode, and RevealJS.