Intro to Git and Github

Welcome!

Welcome!

What we will cover today

What is version control?

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

Version Control Types

Version Control Types

Centralized vs Distributed

Example Workflows

Non linear

Example Workflows

Subversion-style (centralized)

Example Workflows

Integration Manager

Example Workflows

Dictator and Lieutenants

Version Control Distribution

Stack Overflow Developer Survey 2016

Intro to Git

Goals of Git Design

• Fast - Add to your team and code base quickly
• Non-linear - Support for multiple users and sets of changes
• Reliable - Safeguards protect code from corruption
• Distributed - Everyone has a local copy of the history

Without Version Control

With Version Control

Installation and Setup

Git installation instructions on GitHub

Your first Local Repository

Go to home directory

In the bash terminal:

cd ~
          

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

Open hello_world.txt and add some more text

git status
          

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.
            

Nobody's Perfect

Undoing local changes

If you haven't committed yet

git status
git checkout hello_world.txt
git status
            

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 -m "Changing and committing some lines"
git log --pretty=oneline
git revert [HASH]
            

Look at hello_world.txt. Your changes are gone.

Nobody's Perfect

Remove a file from staging

Create new file my_new_file.txt

git add my_new_file.txt
git reset my_new_file.txt
            

Nobody's Perfect

Delete a file

Create new file my_other_file.txt

git add my_other_file.txt
git commit -m "Add new file"
          

Manually delete your file

git rm my_other_file.txt
git commit -m "Remove file"
          

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

Git Branching

Branching

Create a new branch called new-feature

git checkout -b new-feature
          

Add new lines to hello_world.txt

git add hello_world.txt
git commit -m "Adding changes for new feature"
          

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 new-feature and look at hello_world.txt

git checkout new-feature
          

Merging

Merge to get changes from one branch into another*

Switch to master and merge changes

git checkout master
git merge new-feature
          

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 on master"
          

Switch to new-feature branch

git checkout new-feature
          

Open hello_world.txt and change first line

git add hello_world.txt
git commit -m "Changing first line on new-feature"
          

Merging

Merge conflicts, cont.

Merge from master into new-feature

git merge master
          

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

GitHub

• Launched in 2008
• Leader in Social Coding
• GitHub is a commercial site that allows users to host Git repositories publicly and privately
• Open source projects host or mirror their repositories on GitHub
• Post your own code for others to use or contribute to
• Use and learn from the code in other people's repositories

GitHub

Git repository servers

• GitHub
• Bitbucket
• GitLab
• and more!

GitHub

GitHub

ReadME

While a README isn't a required part of a GitHub repository, it is a very good idea to have one. READMEs are a great place to describe your project or add some documentation such as how to install or use your project. You might want to include contact information - if your project becomes popular people will want to help you out.

GitHub

Get Local Repository of GitHub Repo

cd ..
mkdir hello-world
cd hello-world
git init
git remote add origin https://github.com/USERNAME/hello-world.git
git pull origin master
          

GitHub

Push to GitHub Repo

Edit the ReadMe file

git add README
git commit -m "Create readme file"
git push origin master
          

Go look at your github repo online

GitHub

Pulling from remote repository

If you're working with a team, make sure that you have everyone's changes before pushing your own changes.

1. Commit local changes
2. Pull changes other people have made
3. Fix any conflicts and commit
4. Push local changes to GitHub

git commit -m "My latest commit"
git pull origin master
git commit -m "Fixing merging conflicts"
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.

GitHub

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

GitHub

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

Questions?

Resources

Git Basics

Try Git in the browser

GitHub Help

GitHub Cheat Sheet

GDI Survey

Please complete the GDI survey for this workshop.

Click here!