This document provides an overview of revision control systems like Git and GitHub. It discusses what revision control is, some early systems like SCCS and RCS, and then focuses on more modern distributed systems like SVN, Git, and Mercurial. For Git specifically, it covers features like non-linear development, easy branching and merging, auditing of history, and distributed development. It provides instructions for getting started with Git locally and also hosting projects on GitHub. Finally it advertises an additional hands-on training session for working through more examples.

1. Git and Github.com
Jason Noble
instructor@jasonnoble.org

2. What is Revision Control?
• Keeps track of changes over time
• Allows you to go back in time
• Helps prevent code from “disappearing”

3. Revision Control Systems
• cp –R source_dir source_dir-2013.02.20.12.18.52
• Mark Rochkind creates Source Code Control System
(SCCS) in 1972
• Walter Tichy releases Revision Control System (RCS)
in 1982 (still actively maintained)
• CVS introduced in 1986 (handles editing multiple
files at once)
• Commercial systems: ClearCase, VSS and Perforce

4. Revision Control Systems (cont)
• Subversion (SVN) came out in 2000. Designed to be
mostly compatible with existing CVS projects.
– Offers atomic commits (CVS did not)
– Keeps track of file renames and moves
– Branching / Tagging is expensive (copies all files)
– Tags are modifiable

5. Revision Control Systems (cont)
• Git introduced in 2005
– Linux kernel used BitKeeper (commercial
software) because it was free for OSS
– Bitkeeper started charging, so Linus Torvalds
wrote a compatible program (Git)
• Mercurial (similar to Git) was also created
because of the BitKeeper license change

6. Features of Git
• Git has a strong emphasis on non-linear
development
• Branching and merging is easy
• Auditing of history
– If the code in a commit changes, the SHA-1 changes
– Once published, it prevents history changes without
people noticing
• Distributed Development is the #1 selling point

7. Git 101
• Setup central “blessed” repository
– Each developer downloads a copy
– Developer can do local development without
affecting other developers
• Branching is cheap
– git checkout -b branch_name

8. Getting started with Git
• mkdir test_app
• cd test_app
• vi hello_world.rb
#!/usr/bin/env ruby
puts “Hello World”
• git init .
• git status
• git add hello_world.rb
• git commit –m ‘Added hello_world.rb’

9. Github
• Github.com is a website that hosts Git repos
• Allows you to share your code with others
• Easy Forking / Cloning of existing repos
• Provides an easy to use website for hosting
your software projects

10. Create New Repo on Github
• Visit https://github.com
– Login if necessary
• Click New Repository
• Enter repository name, description
• Click Create repository
• Follow directions

11. Additional Hands on Training
• Tonight from 6:30 to 8:30pm
• Bring a laptop with Git installed
• Signup for a Github.com account
• Hands on instructor led tutorial
– TAs will be available to assist
• http://www.meetup.com/DaVinci-
Coders/events/104098422/