Why you should be using a Why you should be using a distributed version control system distributed version control system

(DVCS) for your project(DVCS) for your project

Lenz Grimmer <Lenz Grimmer <lenz@grimmer.com>>

http://lenzg.net/ | Twitter: | Twitter: @lenzgr

2009-12-032009-12-03

SAPO Codebits | Lisbon | PortugalSAPO Codebits | Lisbon | Portugal

Agenda

● Disadvantages of the central approach

● DVCS Concepts and Advantages● Overview: Bazaar, git, Mercurial

$ whoami

1998 2002

2010?2008

Disadvantages of the centralized approach

(e.g. Subversion and CVS)

Most operations require communication with the central

repository

Checkpointing your work requires committing to the

central repository

Branching and merging considered painful

Collaboration is hampered

DVCS: Concepts and Advantages

There is no central instance(Well, duh!)

Disconnected operations

Local commits

Easy branching and merging

Multi-protocol support

Sample workflows

Solo Workflow

● Create project● Commit changes● Review/browse

history● Tag/publish release● Apply new changes● Rinse & Repeat

Hack

Pair programming

Create repository

Branch

HackHackCommit

Pull and merge

Commit

Developer A Developer B

Push, pull, merge

Code deployment

Upstreamproject

Live site

Developer

Branch

Hack

Commit

MergePush

Central Branch & Gatekeeper

Central repository Gatekeeper

Developer A Developer B

Branch, Merge,Pull

Edit, Commit,Push

Merge, ReviewPush

Edit, Commit,Push

Overview: Bazaar, git, Mercurial

Comparison aspects

● Usability differences● Project hosting sites● OS support● 3rd party tools (e.g. IDE integration, GUIs)● Plugins/Extensibility● Speed● Reference projects● Handling of branches and merges

Bazaar

● Python● Sponsored by Canonical● Hosting Platforms: Launchpad | Sourceforge● Many plugins● One branch per directory – simplifies the UI● IDE/GUI support● Strong OS support (incl. Windows)● References: Debian apt, awn, Gnash,

MySQL, Ubuntu

git

● C | Perl | Shell● Originated from the Linux Kernel Community● Speed first, usability later● Powerful, but steeper learning curve● Multiple branches per directory● Platforms: Kenai, github, gitorious,

SourceForge● References: Linux Kernel, Ruby on Rails,

jQuery

Mercurial

● Python● Plugins● Platforms: Bitbucket, Google Code, Kenai● Multiple branches per directory (named

branches)● A „pull“ updates the repo, not the working

copy● References: NetBeans, OpenJDK,

OpenOffice, OpenSolaris, Python

Q & A

Questions, Comments?

Thank you!Lenz Grimmer <lenz@grimmer.com>