Living In A Subversive World

This describes how to use Subversion on a day to day basis. If you have inherited or been assigned to a software development project that uses Subversion, but are unfamiliar with how it works and how to use it, then this post is for you.

So What is Subversion?

Apache Subversion is a Source Configuration Management (SCM) system that has one central repository, usually located on a web server. Each of us works on our own copy of the Subversion-controlled project. When post our changes back to the central repository, Subversion merges them with the existing code and increments the Revision number. Anyone who then updates their local copy of the project will now see the changes we just made. As long as everyone performs frequent updates to their local copy, it all works fine.

What’s So Great About It?

Subversion uses the copy-and-merge philosophy, in contrast with the Lock-Modify-Unlock method used by older SCMs such as RCS, and Microsoft Visual SourceSafe (VSS). In these systems, only one person can change a file at a time, while everyone else is locked out. Veterans of RCS or VSS may point to a risk of running into conflicts and other problems when using Subversion’s copy-and-merge. While the risk of conflicts is still present when two or more people are working on a file, in practice this is only a concern when these people are changing then same part of a file.

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