By Christopher Pezza – Monfort College of Business 2012

An Introduction

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Version Control refers to management of changes to documents, programs, large web sites and other information stored as computer files.

Used in software development, where a team of people may change the same files.

Version Control

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git /'ɡɪt/ -- Git is an extremely fast, efficient, distributed version control system ideal for the collaborative development of software.

Invented by Linus TorvaldsVersion Control Tool

Powerful Flexible Low-Overhead

What is Git?

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VCS Requirements that drove the

development of Git

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Facilitate Distributed Development

Scale to handle thousands of developers

Perform quickly and efficiently

Maintain integrity and trust Enforce accountability Immutability Atomic transactions Support and encourage

branched development Complete repositories A clean internal design Be free, as in freedom

What features or characteristics were missing from pre-Git VCS systems?

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Allow parallel as well as independent and simultaneous development in private repositories without the need for constant synchronization with a central repository

Allow multiple developers in multiple locations even if some of them are offline temporarily

Facilitate Distributed

Development

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Thousands of developers contribute to each Linux release

Handle a very large number of developers, whether they are working on the same or on different parts of a common project

VCS must integrate all work reliably

Scale to Handle Thousands of Developers

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Needs to support a large volume of update operations that would be made on the Linux Kernel

Individual update operations and network transfer operations have to be very fast

To save space and thus transfer time, compression and “delta” techniques would be needed

Perform Quickly and Efficiently

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Git uses a common cryptographic hash function, called SHA1, to name and identify objects within its database

Maintain Integrity and Trust

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Git enforces a change log on every commit that changes a file

Git ensures that changes will not happen mysteriously to files under version control because there is an accountability trail for all changes.

Enforce Accountability

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Once objects have been created and placed in the database, they cannot be modified

Objects can be recreated differently, but the original data cannot be altered.

The entire history stored within the version control database is also immutable.

Immutability

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A number of different but related changes are performed either all together or not at all

Ensures that the version control database is not left in a partially changed (possibly corrupted) state while an update or commit is happening

Atomic Transactions

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VCSs can name different genealogies of development within a single project

VCS can also split a single line of development into multiple lines and then unify, or merge, the disparate threads

Git calls a line of development a branch and assigns each branch a name

Support and encourage branched

development

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In order to avoid individual developers needing to query a centralized repository server for historical revision information, each repository has a complete copy of all historical revisions of every file.

Complete Repositories

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Git’s object model has simple structures that capture fundamental concepts for raw data, directory structure, recording changes, etc.

Coupling the object model with a globally unique identifier technique allowed a very clean data model that could be managed in a distributed development environment.

A Clean Internal Design

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“Free software” means software that respects users' freedom and community.

users have the freedom to run, copy, distribute, study, change and improve the software

Free Software is a matter of liberty, not price: Think “free” as in “free speech,” not as in “free beer”.

Example: GNU Licenses

Be Free, as in Freedom

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social networking functionality such as feeds, followers and the network graph to display how developers work on their versions of a repository.

a pastebin-style site called Gist

wikis for individual repositories

web pages that can be edited through a Git repository

GithubFeatures

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DEMO TIME

Thanks for Watching!

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White, Tom (2011). Version Control with Git: Powerful Tools and Techniques for Collaborative Software Developement. Sebastopol, CA: O’Reilly.

Wikipedia – Git (software) What is Free Software?

From the GNU Project

Sources

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