# Friday, January 21, 2011

This blog post is a repurposing of content I created for a presentation I gave on DVCS on 01-11-2011 to the Twin Cities Developer Group.

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What is DVCS?

Source code version control without a central master server repository (think peer to peer).

Market leaders: git, hg / Mercurial

New competitor with potential: SourceGear Veracity

http://en.wikipedia.org/wiki/Distributed_revision_control

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Is DVCS better than non-distributed source control (aka Subversion/SVN, VSS, TFS, etc.)?

Usually, yes, but there are exceptions.  Don't underestimate the learning curve.

http://stackoverflow.com/questions/111031/comparison-between-centralized-and-distributed-version-control-systems

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What are the Disadvantages of DVCS?

Lack of mature graphical front ends (although people seem okay with TortoiseHg/TortoiseGit), the majority of DVCS users appear to use the command line.

The learning curve for DVCS is different.

There are different complexities like workflow & backup process creation.

Many people struggle with the concept of "no canonical master".

Large binary files don't work well in a DVCS where everyone has a local copy of basically the entirety of every version of every binary file.

There are currently tools to migrate to DVCS, but not necessarily tools to migrate away from DVCS.

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Advantages of DVCS – Better Implementation

What could non-distributed version controls systems do better to compete with DVCS?

  • Implement better merging
  • Implement better handling of versioning directories

What are some of the reasons that merging is better in DVCS?

  • Change sets
  • Likely more version history available to work with since smaller check-ins are better supported
  • Better ancestor tracking/usage
  • Better directory revision management
  • Better file rename detection

The battle is not DVCS (git/hg) vs. SVN, but that is how it is often characterized.  SVN is lacking in some areas compared to it's (sometimes commercial, sometimes more mature) non-distributed version control competitors.

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Advantages of DVCS – Better Design

What can’t non-distributed version controls systems do?

  • Working "offline" (faster history access, faster commits)
  • Better experience working peer to peer for integration testing
  • QA can manage their own repository
  • Can commit a logical unit of work without tests passing or the code even compiling

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DVCS Trends

Where is DVCS catching up?

  • GUIs
  • ALM integration
  • Hard locks
  • User/role permissions
  • Centralized admin, etc.

DVCS in corporations is very interesting to me personally and Veracity will likely solve those problems better than git/hg ever will since they are primarily targeted at open source projects, not corporate/enterprise environments.

Obstacles to an enterprise DVCS - http://www.ericsink.com/articles/vcs_trends.html

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Some differences between Mercurial and Veracity

http://www.capprime.com/software_development_weblog/2011/01/20/SourceGearVeracityMercurialLookupChart.aspx