The document discusses Distributed Version Control Systems (DVCS), detailing their advantages, workflows, and the experiences of the authors, Louis Jacomet and Jo Voordeckers. It includes comparisons between different version control systems such as Git and Mercurial, as well as best practices for managing project workflows and collaboration among developers. Key topics include the importance of revision control, internal workflows, and project hosting options.

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DVCS in practice
JoVoordeckers
jo.voordeckers@pursuit.be
@jovoordeckers
blog.pursuit.be
Louis Jacomet
ljacomet@gmail.com
@ljacomet

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Agenda
‣ Why revision control
‣ DVCS explained
‣ Workflows and practices
‣ What DVCS bring
‣ DVCS Compared
‣ Tools & plugins
‣ Project hosting
‣ Q & A

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About: Louis Jacomet
‣ 2002 - 2009 - Consultant at Axen
‣ 2009 - Freelance at Craft In Development
‣ Relevant experiences:
‣ Banking 2005 - 2008
‣ Migration of repository from Harvest to SVN => Happy Users!
‣ Administration of SVN, including branching and merging strategies
‣ Tried different ways of structuring workflow with branches, reviews,
gates in a team of up to 30 developers where quality was an issue
=> Unhappy Admin in search of a better world
‣ Git user ( mostly in front of SVN) for about a year

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About: Jo Voordeckers
‣ 2002 .. 2005 - Partner at Imagine-IT
‣ 2006 .. 2007 - Senior Software Engineer at Dolmen
‣ 2007 .. 2008 - Technical Project Leader at Dolmen
‣ 2008 - Founded Pursuit Consulting
‣ Java and RIA development contracting & consultancy
‣ iPhone developer: 1 commercial app in the store
‣ User of Mercurial (6 months), SVN (3 years) and CVS (5 years)
‣ Speaker at:
‣ JavaOne, Devoxx, BeJUG, IT Works, SAI

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Why revision control
‣ Tracks history and evolution of software projects
‣ Recover from mistakes
‣ Work on multiple product versions in parallel (prod, features, ...)
‣ (Consistent file set)
‣ Synchronize with collaborators
‣ Backup
‣ Common versioning systems
‣ RCS, CVS, SVN
‣ ClearCase, Perforce, TeamFoundation Server

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http://hginit.com

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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Checking out / Updating

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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DVCS Explained
http://atomiq.org/archives/2004/09/things_you_shouldnt_have_to_explain_to_your_kids.html/

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http://betterexplained.com/articles/a-visual-guide-to-version-control/

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http://betterexplained.com/articles/intro-to-distributed-version-control-illustrated/

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Changesets at the basis
http://hginit.com
http://petevidler.com/series/mercurial/

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Internally it looks like
http://book.git-scm.com/

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Distributed
http://hginit.com
Feature A Repo
Feature B Repo

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Collaborating: where is my commit?
http://hginit.com

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http://hginit.com
Collaborating: where is my commit?

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http://hginit.com
Collaborating: where is my commit?

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http://hginit.com
Collaborating: where is my commit?

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DVCS Sweet spot
‣ A lot faster (10 to 150x)
‣ Very scalable (developers and repo size)
‣ History searching and filtering
‣ Cheap branching, near-instant switching
‣ Effortless merges
‣ Works off-line
‣ As many backups as users (clones) from the central repository
‣ Flexible developer workflow
‣ (Import existing CVS, SVN, … repositories with entire history)
‣ (Metadata is stored in a single .hg or .git folder)

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Effortless merge
merge ?
Base
File edited
File moved

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Workflows and practices
‣ Or how you keep your sanity when you are not alone?

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Internal workflows
‣ Trunk for development or stable only?
‣ Feature branches
‣ Yes or No?
‣ Short or long lived?
‣ Multiple versions
‣ Tags only or branches and hot fixes standard?
‣ How to make sure a fix is everywhere?
‣ Commits
‣ Anyone anytime or reviews and green light?

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Firm and soft branches
release 1
release 2
Trunk
Feat A
Feat A’
F
i
r
m
S
o
f
t

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DVCS and workflows
‣ Internal workflows
‣ All supported
‣ Distributed workflows
‣ Personnal workflow
‣ Merge or rebase

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Distributed workflows
Local Local Local
Adapted from http://http://whygitisbetterthanx.com/
Central

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http://betterexplained.com/articles/intro-to-distributed-version-control-illustrated/

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http://betterexplained.com/articles/intro-to-distributed-version-control-illustrated/

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Distributed workflows
Dictator Blessed
Lieutenant
Lieutenant
Developer Developer Developer Developer
Adapted from http://http://whygitisbetterthanx.com/

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Personal workflow
‣ Your choice
‣ Multiple options available
‣ Allows committing on parallel tasks isolated
‣ Commit is no longer public by default
‣ Choose what goes public
‣ Original workflow
‣ Sanitized workflow

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As before
Hack, Commit, Hack
Fetch
Merge
Push
Hack, Commit, Hack

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Isolated
H.,C.,H.
M
erge
Branch
Fetch Fetch
Merge
back H.,C.,H.
Push

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Topic change
H.,C.,H.
M
erge
Branch
Fetch
H
H.,C.,H.
M
erge
Branch
again
Push

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Social coder
H.,C.,H.
Branch
Fetch
Offer
patch
Clean up
Rebase
Fetch
H.,C.,H.

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Merge or rebase?
http://blog.xebia.com/2010/09/20/git-workflow/

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Git vs Hg

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Git vs Hg
Native code (faster) Python + native code
Linux and MacOS supported
msysgit or Cygwin on Windows
All platforms
easy server on Linux/MacOS
server requires work on Windows
“hg serve” allows serving from
any platform easily
GitX on Mac MacHG
IntelliJ, (Eclipse), (Netbeans) Netbeans, Eclipse, IntelliJ 9

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Git vs Hg
Infers rename/copy by history “hg copy”, “hg rename”
Based on similarity of file content “hg addremove -s”, can also infer
Very good SVN integration,
incompatible with git sharing
SVN integration
Many commands, strange params
Easier to learn, commands match
SVN
Terse manpage doc, improved over
time
Quality and modern docs
Commits identified by SHA1 only
Local human readable ID, global
SHA1

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Git vs Hg
Unlimited parents merge Only 2-way merge
Periodic “git-gc” auto or on demand No maintenance
Private branch namespace + mapping Shared branch namespace
Private user makes public Public history by default
Can destroy history on demand Immutable history,
History usually still accessible except “hg rebase”
Prune to fully delete, explicit

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Git staging area

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Project hosting
‣ Mercurial
‣ - http://bitbucket.org/
‣ - http://code.google.com/hosting/
‣ GIT
‣ - http://github.com/
‣ - http://sourceforge.net/ (supports hg too)

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Finding a revision with bisect
‣ Binary search for a commit
‣ Can be scripted for a fully
automated search

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Git as SVN front-end
‣ Fully clone a SVN repository - might take some time
‣ Full clone of a sub project inside the repository supported
‣ Init and fetch only part of history
‣ Take only a specific path (trunk, a branch, ...)
‣ Note: quite hard to fetch later earlier commits
‣ Daily work
‣ rebase to maintain linear history for commits pushed back
‣ Git does not track directories, so it will not send remove dirs to SVN
‣ enabled through --rmdir

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References
‣ Mercurial
‣ HG Intro - http://hginit.com/
‣ Small project workflow - http://petevidler.com/series/mercurial/
‣ HG book - http://hgbook.red-bean.com/
‣ GIT
‣ GIT Community book - http://book.git-scm.com/
‣ Pro GIT book - http://progit.org/
‣ Google’s Analysis - http://code.google.com/p/support/wiki/DVCSAnalysis
‣ http://betterexplained.com/articles/a-visual-guide-to-version-control/

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