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Git & GitHub Basics

KYOSS Presentation on Git

DVCS for everyone

By: Alan Blount & Jeff Squyres

Oct 2012

http://goo.gl/qr2JS

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Why Is Version Control Important?

We all know about...

but what about this?

FAIL

Version control is important

because "FAIL" happens

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Why Is Version Control Important?

Or more likely, when working on a project

have you ever done anything like this?

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Version Control to the Rescue

A Version Control System (VCS) would fix that

Never lose data
Internal verification on integrity
Historical version retained
History of who did what
Commit messages
Diffs / patches
Branches & tags
Immutable reference

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What is Git?

Git is an open source,

distributed version control system designed for speed and efficiency

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What is Git?

Git is an open source,

distributed version control system designed for speed and efficiency

http://git-scm.com/

Easy to install

(covered later)

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What is Git?

Git is an open source,

distributed version control system designed for speed and efficiency

(almost) everything is local

which means

everything is fast

backups are "built in"

work offline

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What is Git?

Git is an open source,

distributed version control system designed for speed and efficiency

Again, most of your work is local (no network)
Branching & merging is painless (really!)
Pulling from and pushing to remotes, network interactions are compressed and minimal over several possible network protocols (including SSH)

Use it how you want to!

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Enough talking -- let's do Git

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Pre-step 0:

Do you have Git installed?

See if you have Git already installed:

$ which git

git not found

If you see "git not found",

you need to install Git

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Pre-step 1:

Install Git (if necessary)

Linux

Red Hat / Centos

$ sudo yum install git

Debian / Related

$ sudo apt-get install git

OS X

Mac Ports

$ sudo port install git-core

Homebrew

$ brew install git

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Now on to the good stuff...

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Configure your Git

Tell Git who you are

$ git config --global user.name "Bob Smith"

$ git config --global user.email "bobsmith@gmail.com"

Tell Git that you like color

$ git config --global color.ui auto

Tell Git that you like nice diffs

$ git config --global merge.conflictstyle diff3

Content from presentation by Jason Axelson

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Create a local Git repo

Make a directory for all your git repos

$ cd

$ mkdir git

$ cd git

Make a git repo

$ mkdir kyoss-git-workshop

$ cd kyoss-git-workshop

$ git init

Happy

Panda!

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Make some files

Create two text files

$ echo "hello, world" > hello.txt

$ echo "goodbye, world" > goodbye.txt

Let's see what git thinks about these files

$ git status

What does it show?

(notice the pretty colors in the output)

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Tell Git about these files

Tell Git about the "hello.txt" file

$ git add hello.txt

Now run "git status" again

$ git status

What does it show?

Any guesses as to why it says that?

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Tell Git about these files

Tell Git about the "goodbye.txt" file

$ git add goodbye.txt

Now run "git status" again

$ git status

Now git knows about both files

They are in the "Staging Area"

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Now commit the files to the repo

"Commit" (save) both files to the Git repo

$ git commit

You'll be prompted for a comment / message

$ git commit -m "Add hello/goodbye"

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Look at what you've done

What does status say now?

$ git status

All clear!

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What exactly have we done?

Working directory

Git

repo

Git

staging area

git commit

git add

git status

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Now let's change a file

$ echo "hello again" >> hello.txt

What will status show?

$ git status

(notice the pretty color in the status output)

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Umm... what did I change again?

$ git diff

diff --git a/hello.txt b/hello.txt

index 4b5fa63..97a2a03 100644

--- a/hello.txt

+++ b/hello.txt

@@ -1 +1,2 @@

hello, world

+hello again

These numbers will be different for you

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Umm... what did I change again?

$ git diff

diff --git a/hello.txt b/hello.txt

index 4b5fa63..97a2a03 100644

--- a/hello.txt

+++ b/hello.txt

@@ -1 +1,2 @@

hello, world

+hello again

You changed hello.txt by adding one line

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git status and diff

Working directory

Git

repo

Git

staging area

git status

git diff

git diff --cached

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10 rules of committing

1. Always "git status" and "git diff" before commit.

2. Always "git status" and "git diff" before commit.

3. Always "git status" and "git diff" before commit.

4. Always "git status" and "git diff" before commit.

5. Always "git status" and "git diff" before commit.

6. Always "git status" and "git diff" before commit.

7. Always "git status" and "git diff" before commit.

8. Always "git status" and "git diff" before commit.

9. Always "git status" and "git diff" before commit.

10. Always "git status" and "git diff" before commit.

1 rule

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Time to "commit" again

Ok, let's commit our change to hello.txt

$ git commit

$ git commit -m "add more to hello"

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Time to "commit" again

Hey.. why didn't it work?

no changes added to commit (use "git add" and/or "git commit -a")

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Add the change, then commit

Working directory

Git

repo

Git

staging area

git add

$ git add hello.txt

$ git commit

git commit

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Make another change

$ echo "hello hello" >> hello.txt

$ git status

...output...

$ git diff

...output...

All that output makes sense

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Now add, but do NOT commit

$ git add hello.txt

Remember the rule:

Run status and diff before commit!

$ git status

# modified: hello.txt

Ok, that looks good

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Now add, but do NOT commit

$ git add hello.txt

Remember the rule:

Run status and diff before commit!

$ git diff

Wait... what?

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We added the change,

so diff is empty

Working directory

Git

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Let's look at the history / log

See all the commits we've done

$ git log

...lots of output...

The log command has lots of options

$ git log --oneline

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Sidenote: git help

git help is your friend

$ git help

$ git help add

$ git help status

$ git help diff

$ git help commit

$ git help log

When in doubt, git help <foo>

Let's look at the history / log

Show the most recent commit (the "HEAD")

$ git show

Show a specific commit

$ git log 21d0

$ git show 21d0

These numbers will be different for you

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GitHub

The real power of git: its distributed nature

GitHub is a public, free Git repo hosting web site

Everyone has a GitHub account, right?

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What is GitHub?

The reason it's a "Hub" is that if you think about a "Hub and Spokes" topology, you can centralize distribution via GitHub.

GitHub

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GitHub

GitHub has a great web interface

- Create and destroy Git repos

- See git log entries and diffs

- ...etc.

Also accessible via the git CLI interface

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What does GitHub Offer?

- Free for Open public repositories

- Reasonably priced Pay accounts for Private

- Web based code/commit logs & comments

- Basic Issue/Feature tracking system

- Basic Wiki for all projects

- Public, brandable website tied to repository

- Collaboration tools

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Do I have to use GitHub?

No!

GitHub is an excellent solution for some problems, but you can use git:

locally (only)
on your local network
with some other service

There are many alternatives to GitHub�with many feature sets.

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Let's use GitHub!

Create a repository on GitHub

https://help.github.com/articles/creating-a-new-repository

Login to GitHub
Click "Create a New Repo" button (top right)

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Create the GitHub repo

Fill in the repo name

Fill in a description,

select "Public"

Click "Create Repo"

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w00t!

Click to copy the GitHub repo URL to your clipboard

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Tell your local Git repo about your GitHub repo

$ git remote add origin <PASTE>

For example:

$ git remote add origin git@github.com:jsquyres/kyoss-git-repository-github.git

Push to GitHub

The first time you push, you must specify

the remote and the branch

$ git push origin master

Counting objects: 16, done.

Delta compression using up to 8 threads.

Compressing objects: 100% (12/12), done.

Writing objects: 100% (16/16), 1.36 KiB, done.

Total 16 (delta 1), reused 0 (delta 0)

To git@github.com:jsquyres/kyoss-git-repository-github.git

* [new branch] master -> master

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Sidenote: Git branches

This is an advanced topic; we won't cover it tonight.

Suffice it to say that the first push you do to GitHub must be:

$ git push origin master

Git will save that as the default. Subsequently, you can just do:

$ git push

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What just happened?

kyoss-git-workshop

repo

kyoss-git-workshop-github

repo

After the push, the two repos are identical

Local

GitHub

git push

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GitHub web interface

Play around on the GitHub web interface

See the "Files" and "Commits" tabs
Click on individual files
Click on individual commits

Everything you've done in that repo on your local disk is now up at GitHub

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Make a local change

$ echo "bye=sad" >> goodbye.txt

$ git status

$ git diff

$ git commit -a -m "sad panda"

What just happened?

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What just happened?

kyoss-git-workshop

repo

kyoss-git-workshop-github

repo

Local repo has an additional commit

Local

GitHub

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Push that local change

$ git push

Man... that was easy, wasn't it?

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What just happened?

kyoss-git-workshop

repo

kyoss-git-workshop-github

repo

After the push, GitHub also has that commit

Local

GitHub

git push

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Edit files directly on GitHub

Click the "Files" tab

Click hello.txt

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Edit files directly on GitHub

Click the Edit button
Make some changes
Scroll down, type in a commit message
Click the "Commit Changes" button

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What just happened?

kyoss-git-workshop

repo

kyoss-git-workshop-github

repo

GitHub now has a commit

that your local repo does not

Local

GitHub

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How to get that change?

kyoss-git-workshop

repo

kyoss-git-workshop-github

repo

Pull from GitHub to your local repo

Local

GitHub

git pull

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How to get that change?

$ git pull

...lots of output...

$ git show

You'll see the change you made at GitHub

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That's all fine and good, but...

How is this useful to me?

Here's two obvious (single-user) uses:

Backup your files (publicly!)
Synchronize files between multiple machines

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Synchronize your files between machines

Jeff and Alan both keep our shell startup files under version control

When we login to a new machine, we just checkout our .bashrc (etc.) files, and we get our own comfortable environment:

Shell prompt
Shell aliases
.vimrc, .emacs, ...etc.

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Get a 2nd clone from GitHub

You may still have the URL to your github repository in your clipboard...

(go and copy it if you don't)

$ cd $HOME/git

$ git clone <PASTE> my-clone

What did we just do?

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Now we have 2 clones from GitHub

kyoss-git-workshop-github

repo

Local

GitHub

kyoss-

git-workshop

repo

my-clone

repo

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Let's make a change in my-clone

$ cd $HOME/git/my-clone

$ echo yellow >> hello.txt

$ git status

$ git diff

$ git commit -a -m "hello colors"

$ git push

Go browse on GitHub and see that your commit got there

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Pull that change down to kyoss-git-workshop

$ cd $HOME/git/kyoss-git-workshop

$ git pull

$ git show HEAD

w00t!

You have made a change in one repo and synchronized it over to your other repo

Multiple changes

Ok, that was easy enough.

..but what if I make changes in both kyoss-git-workshop and my-clone?

There are two cases

Conflicting changes

The two commits changed the same line(s) in the same file(s)
ADVANCED TOPIC / not covered tonight

Non-conflicting changes

The two commits changed different line(s) in different file(s)

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Non-conflicting changes: 1

$ cd $HOME/git/kyoss-git-workshop

$ echo hello >> hello.txt

$ git status

$ git diff

$ git commit -a -m "hello again"

What just happened?

kyoss-git-workshop-github

repo

Local

GitHub

kyoss-

git-workshop

repo

my-clone

repo

This will merge in the kyoss-git-workshop change

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What just happened?

kyoss-git-workshop-github

repo

Local

GitHub

kyoss-

git-workshop

repo

my-clone

repo

Now my-clone can push

git push

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What just happened?

kyoss-git-workshop-github

repo

Local

GitHub

kyoss-

git-workshop

repo

my-clone

repo

And kyoss-git-workshop can pull

git pull

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Do it yourself

Make a change in my-clone
Commit and push
Make a non-conflicting change in kyoss-git-workshop
Commit
Try to push (and see it fail)
Pull to kyoss-git-workshop
Run "git log --graph" to see how it all merged together
Push from kyoss-git-workshop
Pull to my-clone

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Next Git Workshop Topics

That's it for the very basics.

You are still in for a lot more. Some of the very best features of Git (and some of the trickiest concepts to understand) are yet to come.

stashing, branching and merging
conflict resolution & merge tools
tagging
forking and pull requests
branching models (feature, dev, release)
deployments with git

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Review & Recap - Git Basics

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What Is Git?

Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

Git is easy to learn and has a tiny footprint with lightning fast performance. It outclasses SCM tools like Subversion, CVS, Perforce, and ClearCase with features like cheap local branching, convenient staging areas, and multiple workflows.

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Why Git?

How is it better than <insert favorite repository here>?

Open Source & Stable
Lots of Applications / Integrations
Everything is Local
Git is Small
Git is Fast
Snapshots vs. Deltas
Cheap Local Branching
The Staging Area
Distributed
Any Workflow
GitHub (etc)

(et

Any DVCS system is fine...

Mercurial and Bazaar are also excellent options

(Is it better than SVN/CVS?)

YES!

(e.g., Jeff Mercurial)

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Why GitHub?

GitHub is a convenient option for hosting / sharing

any Git repository.

Cheap or FREE
Good interface for code, commits, diffs
Social and Collaboration integration
Basic issue tracking, wiki, websites

You do NOT need GitHub to use Git.

(et

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Bonus Points

http://gitref.org/ - Git Reference
http://gitready.com/ - Git example walkthroughs, atomic
http://goo.gl/Pw0Fz - Git Cheat Sheet
tig - an excellent CLI interface to look through logs
git-svn - a Git core extension which facilitates integrating Git+SVN
git-wtf - a Git script helping identify branch sync status across multiple remotes