Version Control Systems: git

Andrei Mustață

Software engineer etc
Love me some git

This talk

What VCS are
Benefits of using one
Basic `git`

Version Control System

... version control
"Records changes to a [...] set of files"¹
"recall specific versions later"¹

What is it?

Version Control System

CTRL+Z has its limits
Creates a safe environment for work
Encourages innovation

Why bother?

Version Control System

Google Docs
?

Examples

Version Control System

What?
Why?

Intro - wrap-up

Version Control System

Copy files to separate directories
Timestamp in filenames
Error-prone

Local - manual

Version Control System

File versioning is handled, which is nice
HDD corruption
What about collaboration?

Local - Issues?

Version Control System

Centralised (CVCS)

Version Control System

Files are on a single server
More people can access it
Teamwork makes the dreamwork
Examples: CVS, SVN, Perforce

Centralised (CVCS)

Version Control System

Files are still versioned
Collaboration is allowed
?
Single-point of failure
HDD corruption

Centralised (CVCS) - Issues?

Version Control System

Distributed (DVCS)

Version Control System

More arrows
Clients fully mirror the repo
Server dies, client repos can serve as backups
Allows for different workflows
Examples: git, Mercurial, Bazaar

Distributed (DVCS)

Version Control System

Distributed (DVCS) - git

Created by Linus Torvalds for the Linux kernel
Great for large projects
Great for branching

Version Control System

Distributed (DVCS) - Issues?

?
Surely there are some

Version Control System

Types - wrap-up

Local - manual
Local - using tools
Centralised - server-client
Distributed - server-client-like, but not necessarily

git

How it works
Installation, setup
Most used commands

git

How it works

Snapshots
Most operations are local
Check-sums
Fear of the data-loss
Three states

git

Everything (almost) is local

Most operations are done on the local file system
No network overhead = offline work
Differences in files between now and 7 days ago
Commit away

git

Everything is check-summed

Before storing files, git always check-sums it
Can't change stuff without git knowing about it
SHA-1, based on file content

git

Everything is (pretty) safe

Once the commit has been made, it's pretty safe
It's hard to get git to do things that are not undoable
Freedom to try new things without losing the initial state

git

The three states

Working directory
Staging area
Repository (local .git directory)

git

Basic workflow

Modify files on your machine
Stage the files
Commit

DEMO TIEM

git

Basics - wrap-up

Safety-net
Three states: working, staging, repository
Modify-Stage-Commit

git

Setup

Install - cmd or GUI
SourceTree from Atlassian
Configure user.name, user.email
on you go!

git

Setup

Create an Atlassian (BitBucket) account

git

Local repository

Create your own
Clone an existing one

git

Create local repository

$ mkdir hello-world-git
$ cd hello-world-git
$ git init
$ ls -la

git

Recording changes

staging files
committing files

git

Staging files

$ date >>README.md

$ git stage README.md

git

Committing changes

$ git commit

git

Recording changes

modify (hacky thingy changy)
stage (git stage <filename>)
commit (git commit)
you're done, go home

git

Status

what the repository status is

$ git status

git

Status of a file

Untracked - new file, not added anywhere yet
Staged - file in git staging area
Unmodified - ...
Modified - file is tracked by git; changed

git

Diff

differences

$ git diff

git

Branches

at least one branch, default master
add stuff without interfering with the main branch
allows for experimenting without fear of breaking

$ git branch my-feature

git

Merge

bring changes from a branch into another branch

$ git merge my-feature-branch

git

Clone remote repository

$ rm hello-world-git
$ git clone https://bitbucket.org/andreimic/hello-world-git.git
$ cd hello-world-git
$ ls -la

git clone downloads a full copy of the repository
access to the whole public history of the project

git

Push

don't keep changes to yourself
push to the common git server (remote)

$ # git push <remote> <branch>
$   git push  origin   master

git

Code review

Pull/merge request
Lookie what I did
Comments

git

Less important stuff

ignoring files
hm

but important still

git

Ignoring files

pls no binaries
pls no zip files
.gitignore file
https://github.com/github/gitignore

*.class

# Mobile Tools for Java (J2ME)
.mtj.tmp/

# Package Files #
*.jar
*.war
*.ear

# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
hs_err_pid*