Distributed Version Control Systems in the Enterprise - Atlassian Summit 2010

Distributed Version Control (DVCS) in the Enterprise Justen Stepka, Atlassian 2 2

Agenda • What is DVCS? • Migration case study • Atlassian and DVCS 3 3

What is DVCS? 4 4

Version Control Systems • Popular options • Common Problems • CVS (1990) • Server or network downtimes • Subversion(2000) • Distributed teams have network latency issues • Perforce • Merging between branches is a PITA • ClearCase 5 5

VCS deployments Alice ll Pu Checkout / sh Add Pu Remove Remote Update Central Log Commit Repos. Merge Bob Pull Bamboo 6 6

Distributed Version Control (DVCS) • Popular options • Beneﬁts over VCS • Git • Localized commits • Mercurial • Full revision and branch history locally • Bazaar • No server downtime • BitKeeper (commercial) 7 7

DVCS deployments Alice’s Repos. l Alice l / Pu h us Pull P Add Remove Update Log Bob’s Push / Pull Master Commit Repos. Repos. Diff Merge Bob Pull Pu sh Bamboo Custom Builds 8 8

VCS DVCS Easy branching Easy Branching Core func9onality -‐ tracks your merge history, even Painful merging between ﬁle renames Tool support kicks ass Tool support varies by implementa9on Experiment with local commits and branches, Requires a network connec9on easily rollback changes. Great for distributed teams. Authorita9ve trunk is well known and understood Authorita9ve trunk must be deﬁned and enforced 9 9

Git or Mercurial? 10 10

Git • Great for Linux / Mac • Windows support is limited, but upcoming • 150+ commands, complex for newbies • Developed using C • Used by many open-source projects • GitHub - http://github.com • 11 11

Mercurial • Excellent support across all platforms • An easier learning curve than Git - similar commands to Subversion • Smaller community adoption • Developed using Python - extendable • BitBucket - http://www.bitbucket.org • 12 12

Whoʼs using what? Mercurial Git Adium Android Python jQuery OpenJDK Linux Kernel OpenOﬃce.org Perl Netbeans Ruby on Rails Vim Wine 13 13

Desktop Tool Support Tool Mercurial Git Linux Linux Command line Mac Mac Windows Windows (cygwin) IntelliJ IDEA Mul9ple plugins Na9ve support Eclipse Mul9ple plugins Mul9ple plugins Visual Studio VisualHG (most popular) Mul9ple plugins 14 14

Migration Case Study 15 15

What DVCS should you use? 16 16

Personal preference • “Mercurial is your smart friend who lies to explain things to you. Git is your genius coworker who signs and rolls his eyes every time you ask him a question.” http://thebuild.com/blog/2009/11/04/git-vs-mercurial/ 17 17

WTF is moving to Mercurial Our Team, Website Task Force • 1 dev in Sydney, 2 devs and a graphics designer in San Francisco • 24 hour turn around on bugs, 48 hour turn around on copy changes Larger projects run in parallel to daily updates Problems with Subversion • Maintaining multiple branches is a pain in the ass • Overhead of maintaining branches complicates our ability to have a 24 / 48 hour turn around • Members of the Sydney team are far from the data, slow subversion 18 18

Key reasons for moving to Mercurial 1. Tool and platform support is better 2. Learning curve - the existing command structure mirrors Subversion 19 19

How much code are we talking about? 20 20

Migrating to Mercurial • Mercurialʼs built in ConvertExtension • Converts existing CVS and Subversion repositories into a Mercurial repository • Mercurial hgsubversion extension • Used to mirror and existing Subversion repository • local (ofﬂine) commits • Useful for experimenting • Converts an existing Subversion repository into a Mercurial repository 21 21

ConvertExtension • Built into Mercurial - needs to be enabled in your ~/.hgrc conﬁg • Failed several times processing our Subversion repository • Took ~31 hours to convert 370k lines of code • Does not support the extraction of branch or tag information 22 22

hgsubversion extension • Subversion closing utility • Use Mercurial as a Subversion client • Export your Subversion code to start a new share Mercurial repository • Exports all branch and tag information • 2 hours to convert 370k lines of code • 24 24

Exporting the code to • Your can either setup your own server, or • Experiment with BitBucket as your code hosting provider • branching visualization • user management 25 25

Atlassian and DVCS 27 27

JIRA and DVCS Integrate with FishEye + Alpha support for Mercurial with FishEye May 2010 Git support with FishEye 2.0 June 2009 JIRA FishEye JIRA 4 and 4.1 + Released in Sept 2007 Updated release June 2010, actively developed JIRA Plugin + Released August 2009 JIRA 3.12 and 3.13 JIRA Plugin 28 28

Bamboo and DVCS + Dog-food testing internally Expected in the next release, later this year Bamboo Integration Bamboo 2.2 - 2.5 + Released March 2010 Bamboo GitHub Plugin 29 29

Wrap-up DVCS is a shift in the way we use version control • “Instead of asking what problems it solves, you should be asking what new possibilities it offers” • Git and Mercurial are emerging as the two main standards • Atlassian is going to expand support for Git and Mercurial • Several teams at Atlassian have, or are making the switch to Mercurial • Subversion to DVCS bridges exist if youʼd like to experiment without making the full switch • If youʼre experimenting with Mercurial, use the hgsubversion extension 30 30

Resources • Hg Init: a Mercurial tutorial - http://hginit.com • BitBucket - http://www.bitbucket.org • Github - http://www.github.com • hgsubversion - http://bitbucket.org/durin32/hgsubversion 31 31

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