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 Velocity

How the popularity of different distributed version control systems have changed since 2010.

Installation and Setup

Install git

Alternatively, if you're using a Mac you can use Homebrew

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
# The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|         .       |
|        E .      |
|   .   . o       |
|  o . . S .      |
| + + o . +       |
|. + o = o +      |
| o...o * o       |
|.  oo.o .        |
+-----------------+

Installation and Setup

Copy SSH Key to Clipboard

$ pbcopy < ~/.ssh/id_rsa.pub

This code will copy your SSH key into your clipboard.

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

  $ touch hello_world.txt
  $ 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

  # Open hello_world.txt in your favorite editor and type "Hello!"
  $ 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.
              

Look at our progress, visually

  $ gitk
  # OR
  $ git gui citool
            

Nobody's Perfect

Undoing local changes

If you haven't committed yet

  # change hello_world.txt
  $ 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

Remove a file from staging

Create new file my_new_file.txt

$ touch 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

$ touch my_other_file.txt
$ git add my_other_file.txt
            

Manually delete your file

$ git rm 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

• 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

Create your first repository

GitHub

Create your first repository

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 ../ # Back in root directory
$ mkdir hello-github
$ cd hello-github
$ git init
$ git remote add origin https://github.com/NAME-OF-REPO.git
            

GitHub

Push to GitHub Repo

Edit the ReadMe file

$ touch README.md 
$ git add .
$ git commit -m "Adding readme file"
$ git push -u origin master
            

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 
            

Forking

• There are MILLIONS of public repositories on GitHub
• If you want to use or contribute to a repository, you can fork it.

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

$ 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

Starting a pull request

Previewing and sending 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