Intro to Git and Github

Welcome!

Welcome!

What we will cover today

• What is version control and why should we care?
• Basics of git -- the essential commands
• "Gitting" social with Github

What is version control?

Version control allows you (and your team) to do two powerful things

Working without Version Control

The Horror!

Working with Version Control

Rainbows and bunny rabbits!

Brief history of Version Control

1990s -- CVS (Concurrent Version Systems)

2000s -- SVN (Apache Subversion)

2005 -- Git (well, Git)

Version Control Types

Version Control Distribution

Version Control Distribution Change

Intro to Git

Goals of Git Design

• Fast -- add to your team and code base quickly
• Distributed (see slide above)
• Each commit has a corresponding hash (track changes from everyone)
• Everyone has a local copy of the history

Git vs Github

Git is not the same as Github

Installation and Setup

Install git

http://git-scm.com/downloads

*Note for Windows Users: use Git Bash instead of Terminal

Installation and Setup

Setup ssh keys

           $ cd ~/.ssh
          

$ ssh-keygen -t rsa -C "your_email@example.com"
# Generating public/private rsa key pair.
# Enter file in which to save the key (/Users/you/.ssh/id_rsa): [Press enter]
          

Enter passphrase (empty for no passphrase): [Type a passphrase]
# Enter same passphrase again: [Type passphrase again]
          

Installation and Setup

Get SSH Key

Your identification has been saved in /Users/you/.ssh/id_rsa.
# Your public key has been saved in /Users/you/.ssh/id_rsa.pub.
# The key fingerprint is:
# 01:0f:f4:3b:ca:85:d6:17:a1:7d:f0:68:9d:f0:a2:db your_email@example.com
          

Installation and Setup

Add SSH Key to Github

Installation and Setup

Setup name and email in gitconfig

$ git config --global user.name "Your Name Here"
# Sets the default name for git to use when you commit
          

$ git config --global user.email "your_email@example.com"
# Sets the default email for git to use when you commit
          

$ git config --list
          

Your first Local Repository

Go to home directory

cd ~/
OR
cd Users\username
          

Create a "working directory"

mkdir my-first-repo
cd my-first-repo
          

Initialize repository with Git

git init
git status
          

Add files

Create a new hello_world.txt file in your new folder

Check repo status

git status
          

Tell Git to track our new file

git add hello_world.txt
git status
          

File is now tracked by Git

Changes and commits

Stage and commit the change

git add hello_world.txt
git commit -m "First commit. Added hello world to repository."
          

What did we just do??

How is this all different than just saving a file?

• When we add a new file, we tell Git to add the file to the repository to be tracked
• When we stage an existing file (also with the keyword 'add'), we are telling Git to track the current state of our file
• A commit saves changes made to a file, not the file as a whole. The commit will have a 'hash' so we can track which changes were committed when and by whom.

Look at our progress

git log
          

commit [HASH HERE]
Author: Your name 
Date:   [DATE HERE]

    First commit. Added hello world to repository.
            

Look at our progress, visually

gitk
          

Problem?

-bash: gitk: command not found
          

Nobody's Perfect

Undoing local changes

If you haven't committed yet

git checkout hello_world.txt
            

Look at hello_world.txt. Your changes are gone.

Nobody's Perfect

Undoing staged changes

git add hello_world.txt
git reset HEAD hello_world.txt
git checkout hello_world.txt
            

Look at hello_world.txt. Your changes are gone.

Nobody's Perfect

Undoing committed changes

git add hello_world.txt
git commit -am "Changing and committing some lines"
git log --pretty=oneline
git revert [HASH]
            

Look at hello_world.txt. Your changes are gone.

Nobody's Perfect

Delete a file

Create new file my_other_file.txt

git add my_other_file.txt
          

Manually delete and stage your file

git rm -f my_other_file.txt
          

Branching

• Develop different code on the same base
• Conduct exploratory work without affecting the work on master branch
• Incorporate changes to your master branch only when you are ready

Branching

Create a new branch called version2

git checkout -b version2
          

Add new lines to hello_world.txt

git add hello_world.txt
git commit -m "Adding changes to version 2"
          

Branching

Switching branches

See all branches. Branch with * is active

git branch
          

Switch to master and look at hello_world.txt

git checkout master
          

Switch to version2 and look at hello_world.txt

git checkout version2
          

Merging

Merge to get changes from one branch into another*

Switch to master and merge changes

git checkout master
git merge version2
          

*rebase is another option, but will not be covered in this workshop

Merging

Merge conflicts

Change first line in hello_world.txt in master branch

git add hello_world.txt
git commit -m "Changing first line in master"
          

Change first line in hello_world.txt in version2 branch

git checkout version2
# open hello_world.txt and change first line
git add hello_world.txt
git commit -m "Changing first line in version2"
          

Merging

Merge conflicts, cont.

Merge from master into version2

git merge master
          

You will be notified of a conflict. Go to the file and fix the problem. Then commit your edits.

GitHub

Create your first repository

GitHub

Create your first repository "my-first-repo" on Github!

GitHub

Add this Github version as a remote branch called 'origin'

git remote add origin git@github.com:username/my-first-repo.git
git push -u origin master

GitHub

Pushed to Github!

Go look at your Github repo online!

GitHub

Pulling from remote repository

If you are working with a team, you want to make sure that you have everyone's changes before pushing your changes to the GitHub repo

# Commit local changes
git commit -m "My latest commit"
# Pull changes other people have made
git pull origin master
# Fix any conflicts (see merge conflicts above) and commit
git commit -m "Fixing merging conflicts"
# push local changes to GitHub
git push origin master
          

Forking

• There are MILLIONS of public repositories on GitHub
• If you want to use or contribute to a repository, you can fork it.
• Summer of Open Source Projects:
  • VA Digitization
  • Philly Open Health
  • Unlock Philly
  • Open Tree Map
  • School District of Philadelphia Budget Visualizations

Forking

Forking & Cloning

Clone to get a local repository of your fork

cd ../
git clone https://github.com/username/FORKED-REPO-NAME.git
cd FORKED-REPO-NAME

## GET THE ORIGINAL REPO'S URL!!
git remote add upstream https://github.com/original-username/FORKED-REPO-NAME.git
# Assigns the original repository to a remote called "upstream"

git fetch upstream
# Pulls in changes not present in your local repository, without modifying your files
            

Pull Requests

• After you fork and clone a repository all pushed changes will go to your fork
• These changes will not affect the original repository
• If you would like to get your changes to be incorporated into the original repo, you can submit a pull request

Make a change to your forked repo

• Open a file in the repository such as README.md with your text editor (or on Github)
• Fix a typo or add a helpful link
• Make a commit (and push)

Starting a pull request

Preview and create pull request

Managing pull requests

How to manage pull requests is out of the scope of this short workshop, but you can learn more from the Github Collaborating Tutorials

Resources

• Beautiful graphical representation of git features
• Practice with the Githug Game!
• GIT THE BOOK (Free online edition)
• Git Workflow

Questions?