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Intro to Version Control Using Git

Marylou Lenhart

Introductions

Please ask questions.

Goals for the class

Basic understanding of what version control is
Basic understanding of what git is and how to use it
Knowledge of github and what it provides us
Knowledge of the command line interface

Version Control System

A tool that assists in the management of changes to documents.

What does that mean?

You can make changes to documents and save those changes.
You can undo changes
You can include changes from other people*
You can see multiple change-sets simultaneously*

Not just for programming

Anytime you are working on any set of documents that you are making changes to and want to save the state of, version control is extremely useful.

Git

A distributed version control system.

Distributed, in this case, basically means that we can have the same file existing in multiple locations

GitHub

A web service for programming projects that use Git.

Many Open Source projects hosted here

Collaboration

Git makes collaboration easy
GitHub makes collaboration even easier
Easy to copy existing code, update, and share updates with others

Tool Check

GitHub

If you haven't already create a GitHub account at github.com
Login to your account
(optional) Set your avatar at gravatar.com
View your GitHub profile page:
http://github.com/your_username

note: for gravatar use the same email your signed up for github with.

Using Git in the CLI

Learning the Command Line Interface (CLI) for Git pays off in the long run.

Tool Check

Downloading Git

Tool Check

Open the Terminal

On Mac: Applications > Terminal
On Windows: Start Menu > All Programs > Git > Git Bash

ls

cd

Repository

Where our files live

Also referred to as a repo for short.

Contains:

A record of the changes made to those files
Who made those changes
When those changes were made

Activity

Our first repository

Go into our Github account in the browser

Activity

Creating a new repository

Create a new repository

Activity

Creating a new repository

Activity

SSH Key

Type in the terminal:

ls -al ~/.ssh and type enter
ssh-keygen -t rsa -C "email@example.com" and type enter
pbcopy < ~/.ssh/id_rsa.pub and type enter
Reference

Activity

SSH Key

Activity

Creating a new repository

Activity

Our first repository

Go back to the terminal (Mac) or bash (Win)
Type git clone _paste_your_url_here_
Press enter
Go into the newly created directory by typing
cd _name_of_your_repo_

ls

Commit

To save the state of a single or collection of changes.

How to make a commit with git

Whenever you make a change inside the folder where your repo is, git notices and will let you know what files have been changed. Making a commit will then require a commit message.

Git Status

Commit Message

A note that describes what the commit is about.

Bad Commit Messages

Whoops
Fixed a thing
I have no idea
Everything works now
I am so angry at the universe right now

Better Commit Messages

Added the missing read-me file
Fix: Extraneous semi-colon removed
Moved the cat-pix folder inside the images folder
Resolved the problem where content would not display
Added a hack in the CSS to fix the bug with IE
Writing Good Commit Messages

Things to keep in mind

Avoid being vague
Realize that not only are you communicating with future-you, but potientially others
When you can, focus on why you did something not what you did

Activity

First commit

Open up the file named "README.md" inside the directory you just created, make a change, and save it.
Commit your changes:
Type git add README.md
Type git commit -m "Your Commit Message"
Make sure to provide a good description for your commit
And remember to put your commit message in quotes

Syncing your changes

Also known as pushing in the command-line world

Takes the changes you made on your computer and sends them off to the GitHub website

Activity

Sync your changes

Type git push origin master
View the changes on GitHub:
https://github.com/[username]/[repo name]

A quick note on READMEs

README files are generally provided with software or other files that provides information for the person opening it.

They can contain:

How to use a piece of software
Who made the software
Any bugs in a chunk of software

According to the jargon file the name comes from Lewis Carroll's Alice's Adventures In Wonderland when she encounters "Eat Me" and "Drink Me"

READMEs on GitHub

Always will display on the main page on the repo
Are important to those viewing the project so they can see what it is about and how to use it
Supports the ability to make the content appear with styling using MarkDown
Example: reveal.js README

MarkDown

An extremely lightweight markup language.

Reference

MarkDown Example

# Title

* item 1
* item 2
* item 3

*italic text* __bold text__

You Don't Have to Use MarkDown

Plain text will still display perfectly fine

Activity

Add some content to your README

Open "README.md" in a text editor
Add any content that you desire with or without MarkDown
Commit your changes
Make sure to provide a good description for your commit
View your new README on the GitHub website
https://github.com/[username]/[repo name]

Commits don't need all files

We can tell git that we only want to commit changes to some files rather than all.

When do we want to only commit some files?

If we don't want to save our changes in other files.
If the other files are in some broken state.
If the other files are still "works in progress".

How do we commit only files we want?

We only add the files we want!

Activity

Commit only one file

Create "NewFile.md"
Make some changes in "README.md"
Add only "NewFile.md" and then commit.
Then only this file will show up in the list of changes.

Branch

Where your changes live.
By default you start out in the master branch
Difference branches are like parallel universes: they may be very different from one another or very similar and they exist at the same time.

Creating a new branch

When we create a new branch we keep all the old files as is, but are able to make changes that don't affect the master branch.

Why would we do this?

Working on code we are unsure is correct.
(e.g. bug fixes)
Working on a completely new version of something.
Working on a specific feature we want to add.

How do we create a new branch in Git?

How do we view a different branch on GitHub.com?

Activity

Creating a new branch

Create a new branch named "song"
git checkout -b song
Add any song lyrics to your "README.md" file
Commit your changes
Push your changes
View your README on the GitHub website
https://github.com/[username]/[repo name] note: it will still look the same
Change branches on the github website and now look at your README.md file.

Merging

When we take the changes of one branch and pull them into a second branch.

When do we want to merge?

When we have tested our new bug fixes and want to use it.
When we are ready to go live with new features.
When we are ready to go live with a new version.
When we want to combine two new features together.

How do we merge in Git?

Activity

Merging a branch

Merge the song branch into the master branch
Type git checkout master
Type git merge song
Commit your changes
View your README on the GitHub website
https://github.com/[username]/[repo name] note: it should now have your song lyrics

Rolling back commits

Sometimes you want to undo a commit, but still keep your changes.

How do we roll back in Git?

Activity

Resetting some changes

Open "README.md" and add "Changes I don't want" to it.
Commit your changes.
Reset that commit
git reset --soft HEAD~1
git status

Reverting a commit

Sometimes you want to completely undo a commit.

How do we revert in Git?

Activity

Resetting some changes

Open "README.md" and add "Changes I don't want" to it.
Commit your changes.
Reset that commit
git reset --hard HEAD~1
git status

Further Learning

Code School - Try Git (command-line based tutorial)
Git's official documentation
Git Immersion a git walkthrough from the command-line
Deliberate Git a talk about writing good commits

THE END

Thank you!