Distributed Versioning Tools, BeJUG 2010

Craft In Development

DVCS in practice

Jo [email protected]

@jovoordeckersblog.pursuit.be

Louis [email protected]@ljacomet

mailto:[email protected]





Agenda‣ Why revision control

‣ DVCS explained

‣ Workflows and practices

‣ What DVCS bring

‣ DVCS Compared

‣ Tools & plugins

‣ Project hosting

‣ Q & A


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


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



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


http://hginit.com

http://hginit.com/

http://hginit.com/


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




Checking out / Updating
























DVCS Explained

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








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




Changesets at the basis

http://hginit.comhttp://petevidler.com/series/mercurial/

http://hginit.com/

http://hginit.com/

http://petevidler.com/series/mercurial/



Internally it looks like

http://book.git-scm.com/




Distributed

http://hginit.com

Feature A Repo

Feature B Repo

http://hginit.com/

http://hginit.com/


Collaborating: where is my commit?

http://hginit.com

http://hginit.com/

http://hginit.com/


http://hginit.com


http://hginit.com/

http://hginit.com/


http://hginit.com


http://hginit.com/

http://hginit.com/


http://hginit.com


http://hginit.com/

http://hginit.com/


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)


Effortless merge

merge ?Base

File edited

File moved


Workflows and practices

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


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?


Firm and soft branches

release 1

release 2

Trunk

Feat A

Feat A’

Firm

Soft


DVCS and workflows

‣ Internal workflows

‣ All supported

‣ Distributed workflows

‣ Personnal workflow

‣ Merge or rebase


Distributed workflows

Local Local Local

Adapted from http://http://whygitisbetterthanx.com/

Central

http://hginit.com/

http://hginit.com/










Distributed workflows

Dictator Blessed

LieutenantLieutenant

Developer Developer Developer Developer

Adapted from http://http://whygitisbetterthanx.com/

http://hginit.com/

http://hginit.com/


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


As before

Hack, Commit, Hack

Fetch

Merge

Push

Hack, Commit, Hack

Hack, Commit, Hack


Isolated

H.,C.,H.

Mer

ge

Hack, Commit, Hack

Branch

Fetch Fetch

Mergeback H.,C.,H.

Push


Topic change

H.,C.,H.

Mer

ge

Hack, Commit, Hack

Branch

Fetch

H.,C.,H.

H.,C.,H.

Mer

ge

Branchagain

Push


Social coder

H.,C.,H.

Hack, Commit, Hack

Branch

Fetch

Offerpatch

Clean up

Reba

se

Fetch

H.,C.,H.


Merge or rebase?

http://blog.xebia.com/2010/09/20/git-workflow/




Git vs Hg


Git vs Hg

Native code (faster) Python + native code

Linux and MacOS supportedmsysgit or Cygwin on Windows

All platforms

easy server on Linux/MacOSserver requires work on Windows

“hg serve” allows serving from any platform easily

GitX on Mac MacHG

IntelliJ, (Eclipse), (Netbeans) Netbeans, Eclipse, IntelliJ 9


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


Git vs HgUnlimited 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


Git staging area


Project hosting‣ Mercurial

‣ - http://bitbucket.org/

‣ - http://code.google.com/hosting/

‣ GIT

‣ - http://github.com/

‣ - http://sourceforge.net/ (supports hg too)

http://bitbucket.org/

http://bitbucket.org/

http://code.google.com/hosting/

http://code.google.com/hosting/

http://github.com/

http://github.com/

http://sourceforge.net/

http://sourceforge.net/


Finding a revision with bisect‣ Binary search for a commit

‣ Can be scripted for a fully automated search


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


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/

http://hginit.com/

http://hginit.com/



http://hgbook.red-bean.com/

http://hgbook.red-bean.com/



http://progit.org/

http://progit.org/

http://code.google.com/p/support/wiki/DVCSAnalysis

http://code.google.com/p/support/wiki/DVCSAnalysis




Technology

Distributed Versioning Tools, BeJUG 2010