The Data Analysis Tools Series at the Berkeley Institute for Data Science

Git and GitHub -- Ciera Martinez and Matthias Bussonnier

February 21, 2017 at 5-6:30pm in BIDS, 190 Doe Library

Git and Github

Introduction to Git and GitHub

Wether you are lost in the woods trying to save a bear cub stuck in a tree, or defending earth against alien invasion, git is a tool of choice to collaborate and save your progress to come back in time and save the day again if needed.

Though using git (and GitHub) can be quite intimidating or look like dark magic. We will gently introduce you to simple git concept, from Just memorize these shell commands, to some dark voodoo allowing you to do a 66 way Cthulhu merge.

We will learn wether or not Linus Torvald (Git Creator) actually said the following statemnts or not, and wether the following statement have a bit of truth in them:

“all meaningful operations can be expressed in terms of the rebase command”

[git is] so hard to use, but that turns out to be its big appeal

It is true that actual manual page, can be hard to distinguish from markov-chain text, but you probably don’t need to dive into it now.

What we’ll do

The basics

We’ll start pretty soft. Make sure you have git installed, and that it works.

We’ll make sure you know the basics to already use git on your own, and to be ready to collaborate.

What is the difference between github and git?

Git

A lightweight version control system to track changes made to a project through time. There are many ways to use Git on your computer.

The main ways are:

Suggestion: Command Line

Command line is the most popular way to use git, therefore you can get help easily. If you know how to run the command line version, you can probably also figure out how to run the GUI version, while the opposite is not necessarily true. Dont let your inexperience with command line stop you, you only need to learn the very basics of unix to use git.

Github - Remote Hosting

While Git stands alone as a system, Github is a website that hosts your project and Git history. You can use for collaboration, back-up, sharing, and learning. Github is just one of many places to host repositories.

The main ways are:

Suggestion: Github

The benefit of Github is that it is the most popular and has many tools to make it easy and fun to use. The main downside is that it does not allow free private repositories.

Why use Git?

Learning Git

Learning git well is hard, but I would say only 5% of people who use git know exactly what they are doing.

Why is learning git hard?

Demo (Beginner)

Requirements

Git

Try to have git installed on your laptop before coming to the hacker within. If you are on windows we recommend git-bash, which should be bundled with GitHub for Desktop.

Git should be bundled on recent Macs, you can also install it with GitHub for Desktop, or Homebrew.

User of linux probably already have git installed as well , or know how to install it with your favorite package manager.

Activity

Basically we are all going to make a small edit to a file in a repository using basic git commands. Here is an overview with many of the command we will use:

  1. Go here: https://github.com/iamciera/THW_attendence
  2. Press the Fork button (you’ll need a Github account)
  3. In your terminal, execute git clone https://github.com/YOURUSERNAME/THW_attendence. Make sure you replace “YOURUSERNAME” with your Github name. For example mine is iamciera.
  4. Enter the new directory with cd THW_attendence
  5. Add the original remote repo with git remote add upstream https://github.com/iamciera/THW_attendence
  6. Fetch information about the remote with git fetch upstream
  7. Now, you need to check what branch you’re in git branch. Make sure you are on the master branch.
  8. Now we are ready to edit the file. Open the README.md file and add your name to the list. Add under the header of the letter your first name starts with. This is so we avoid merge conflicts.
  9. Commit them. git commit -am "I added files for the tutorial on my topic.." NOTE: -am means you are telling git to “stage all changes in the directory” and that you want to include a commit message
  10. Git push to your origin (your repo on Github) with git push origin master
  11. Navigate in your browser to: https://github.com/YOURUSERNAME/THW_attendence and press the pull request button.

Demo (Advanced)

Advanced tactics !

Narrow down a bug ? Let’s bisect. Want to hide your mistakes ? rebase/amend. Have erased a mistake from history that was not a mistake ? reflog to the rescue.

Blips and Chitz !

Git is no fun without all the configuration option and tricks that make your life easier.

Checkout a PR by it’s number ? oowee! Diff words instead of lines ? Can doooo ! Local and global gitignore ? Sure !

DON’T PANIC

Even if it looks insanely complicated to operate and and partly to keep intergalactic travelers from panicking we’ll discuss what to do when things go south.

Long story short, keep calm and commit -A (and push) if you are really scared. Nothing is ever lost.

What happen in case of broken whatever ? If you are in “Detached head state”, “merge conflict”, or anything else ? We got you covered !

Resources

Examples of how I use Github

Learning Git

Adventure time prompt

Inspired from stackoverflow


function we_are_in_git_work_tree {
    git rev-parse --is-inside-work-tree &> /dev/null
}

function parse_git_branch {
    if we_are_in_git_work_tree
    then
    local BR=$(git rev-parse --symbolic-full-name --abbrev-ref HEAD 2> /dev/null)
    if [ "$BR" == HEAD ]
    then
        local NM=$(git name-rev --name-only HEAD 2> /dev/null)
        if [ "$NM" != undefined ]
        then echo -n "@$NM"
        else git rev-parse --short HEAD 2> /dev/null
        fi
    else
        echo -n $BR
    fi
    fi
}

function parse_git_status {
    if we_are_in_git_work_tree
    then 
    local ST=$(git status --short 2> /dev/null)
    if [ -n "$ST" ]
    then echo -n "| (• ︵•)| (❍ᴥ❍ʋ) "
    else echo -n "| (• ‿ •)| (❍ᴥ❍ʋ)"
    fi
    fi
}

function pwd_depth_limit_2 {
    if [ "$PWD" = "$HOME" ]
    then echo -n "~"
    else pwd | sed -e "s|.*/\(.*/.*\)|\1|"
    fi
}

export PS1="\[\033[32m\]\w\[\033[33m\]\$(parse_git_status)\[\033[00m\] $ "

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