Getting Git

Getting Git
Webuquerque, April 2011

Who am I?
Brian Arnold
(Upper left)

Software Engineer 
for SitePen, Inc.

JavaScript fanatic

Technology 
evangelist

Who are you?
A developer/designer who's lost work 
before
A freelancer who needs to manage a 
wide variety of projects
Someone to heckle me, asking me if I 
used jQuery to make this 
presentation

Version Control!
What is it? Why do I care?

Version Control
Proper definition:
Version control is a means of 
managing a set of files, typically 
code or markup of some sort, managed 
as repositories of code
Varieties of version control 
systems:
Ad‐hoc, Centralized, Distributed
A wide variety of choices

Ad‐hoc
This works... 
sort of

Easy to lose 
work

Hard to 
manage

Centralized VCS
Requires a central server (and 
therefore typically network access 
to said server)
Clients (that'd be you) typically 
get a copy of the latest version of 
the repository's contents
Depending on implementation, files 
may be checked out or locked while 
working on them

Centralized VCS

CVS (1990)
Microsoft Visual SourceSafe (1994)
Subversion (2000)

Distributed VCS
Client typically makes a copy of the 
entire repository to their system
Most actions are local to your 
system, not network‐based
Possible to have a centralized 
shared repository to facilitate 
multi‐user work

Distributed VCS

Git (2005)
Mercurial (2005)
Bazaar (2007)

Choose Wisely!
Centralized systems can be simpler 
to manage
Distributed much easier to use on 
smaller scale
Think about your needs ‐ don't just 
bash something because it's not cool

So then...
Why am I talking about Git?

A Solid Choice

Git is a distributed version control 
system (DVCS)
Immensely popular, used to manage a 
ton of popular open source projects
Fantastic educational materials

What's special?
Stores snapshots of files
(NOT differences)
Nearly every operation is local
(no server needed!)
Written to be strong against 
corruption of data while being 
highly performant

Fscking Git, how 
does it work??
Git is somewhat like a self‐
contained file system, with three 
distinct areas:
Working directory
Staging area
Repository

Working Directory

Your main working area for files
Just a directory
Has the most recent version of the 
code

Staging Area
Internal to Git
Has copies of files that are being 
set up to be pushed into the 
repository
Files can be added and removed 
before being committed into the 
repository

Repository
The .git directory
All of Git's metadata, objects, and 
database are stored in here, after 
they've been staged and committed
Here there be Dragons (don't alter 
files in this directory directly)
Often referred to as a Repo

Getting Git!
By which I mean,
installing it in some fashion,
not comprehension,
that's later

http://bit.ly/SetUpGit
Will send you to help.github.com for your OS

Global Config
The dollar sign in their instructions 
represents the prompt ‐ don't actually 
type it out

The steps walk you through setting up 
some configuration that is GitHub‐
specific

The global config is not GitHub‐specific

Do set your user.name and user.email 
configuration pieces before you start up 
a repository, as per instruction

Getting Git!
Okay, now we're talking comprehension

Goals
How to start using Git as an 
individual
Comfort with creating your own repo
(Hopefully some) comfort with 
branching and merging
Feeling excited for Git!

git init
Setting up your repo

git init

That's it
No, really, that's it
You now have a Git repository!

git status
Checking in on your repo

git status
A useful command to check the status 
of your current workspace, as well 
as staging area
Gives you useful information as to 
actions you can take
We'll be using this command often 
throughout the presentation

git add
Setting the stage for your repo

git add
Add files to the Staging Area (prep 
for being put in the repository)
Marks files to be tracked by Git 
when they are staged for the first 
time
Will work recursively through 
directories
Often people run `git add .` to set 
up all files

HOLD UP!
What if I don't want all the files?

.gitignore

A special file to Git
Put at the root of your working 
directory
List files and patterns you want to 
ignore

git diff

Shows you changes in your files that 
have not been staged
If a change is staged, it won't show 
up in a git diff unless you use the 
‐‐cached option after the command

git commit
Actually putting files
into the repository

git commit

Moves files from the Staging Area 
into the Repository
Accepts a Commit Message
Messages are important!
Succinctly describe the changes 
you're committing

git commit
Use the ‐m command to add a message:

git commit ‐m "My message"

You can skip adding, and just commit 
all tracked files with ‐a:

git commit ‐am "Several changes"

Message about 
messages
Please, please write good commit 
messages
Important for looking back in the 
history of your repository
Makes it easy for the moron who's 
stuck maintaining your work later
(You're often that moron, so be nice 
to yourself)

WOO!
WE HAVE CODE SAFELY STORED!

Keep doing it!
The most basic and standard Git 
workflow
Work on your files
Choose which ones to commit with 
git add
Properly put them in the repo with 
git commit

Time passes
Like sands through the hourglass

git log

A simple, straight‐forward command 
with a lot of power to review what 
you've done with Git
Takes a few options to display 
information in a variety of ways

EXCITING!
Well, okay, not.

Let's look at a real example.

git log

Some parameters that can be used:
‐p : shows the difference
‐# : limits results to last # logs
‐‐pretty : Can change format of 
output
‐‐graph : Can draw branch graphs

git log ‐‐pretty=oneline

git log ‐‐pretty=oneline ‐‐graph

git log

There are tons of ways to look at 
your data
This command is part of why good 
commit messages are important
With poor messages, your log can 
wind up worthless

Branching!
But first, some details about Git that 
we'll need to understand branching.

Would this be a branch...
about branches? #rimshot

I'll be here all night!

What is a commit?
A container of 
metadata Commit

Has a pointer to 
the directory 
snapshot

Has zero or more 
pointers to 
parent commits Snapshot

C1

Each time you 
commit, the new 
commit records 
which one came 
before it

C1 C2

Each time you 
commit, the new 
commit records 
which one came 
before it
C3

What is a branch?
master
A branch is 
nothing more than 
a pointer to a 
commit

In fact, you 
always have one 
C3
branch at first:
master

Another 
visualization

Courtesy of progit.org

git branch
Managing your branches

git branch

With no additional options, it will 
list all of your branches, starring 
the one you're currently on

git branch

When provided with a word after the 
command, it creates a branch with 
that name

git branch

So, how does Git know what branch 
you're on?
Git maintains another pointer, 
called "HEAD", which points at the 
branch you're on
This makes more sense with a 
graphic, so let's see one

git checkout
How to move from branch to branch

git checkout

To move from one branch to another, 
simply run `git checkout branchname` 
where branchname is the branch you 
want to move to
If you want to create a branch at 
the time of checkout, run it with 
the ‐b option:
git checkout ‐b newbranch

git checkout

Once you've switched to another 
branch, you can start working like 
you normally had been
Use `git add` and `git commit` like 
before

Moving around

You can work on multiple branches in 
tandem
Don't be afraid to branch ‐ as 
they're just pointers, the overhead 
for using branches is very low

git merge
Getting the code back together

git merge

When given the name of a branch, it 
does its best to intelligently sync 
up file changes
If possible, it simply moves 
pointers forward

git merge

If it can't just fast forward, git 
will create a new commit that points 
back at the merge bases
Git will do its best to 
intelligently merge the two commits, 
and it generally does the right 
thing
Sometimes, though, we don't

git merge

In order to fix a conflict, open 
your file and look for the <<<<<< 
line
It will show you what conflicted ‐ 
clean up, save, and git add the file 
to mark the conflict as resolved

Homework
Because we all love homework!

Homework

Go install Git on your system:
http://bit.ly/SetUpGit
Set up a GitHub account while you're 
there
Go read http://progit.org/book/
Try Git out on your next project!

Questions!
Like we have time for questions.
This is slide 110!

Thank you!
Talk to me:
brianarn@gmail.com
@brianarn on Twitter/GitHub
Rate me:
http://spkr8.com/t/7087
View this presentation's repo:
https://github.com/brianarn/
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