Subversion for CVS Users

working copy appropriately, adding and removing components.

Subversion defines modules as a list of directories within a directory property: see the section called “Externals Def- initions”.

Authentication

With CVS's pserver, you are required to “login” to the server before any read or write operation—you even have to login for anonymous operations. With a Subversion repository using Apache httpd or svnserve as the server, you don't provide any authentication credentials at the outset—if an operation that you perform requires authentication, the server will challenge you for your credentials (whether those credentials are username and password, a client certificate, or even both). So if your repository is world-readable, you will not be required to authenticate at all for read operations.

As with CVS, Subversion still caches your credentials on disk (in your ~/.subversion/auth/ directory) unless you tell it not to by using the --no-auth-cache switch.

The exception to this behaviors, however, is in the case of accessing an svnserve server over an SSH tunnel, using the svn+ssh:// URL schema. In that case, the ssh program unconditionally demands authentication just to start the tunnel.

Converting a Repository from CVS to Subversion

Perhaps the most important way to familiarize CVS users with Subversion is to let them continue to work on their projects using the new system. And while that can be somewhat accomplished using a flat import into a Subversion repository of an exported CVS repository, the more thorough solution involves transferring not just the latest snapshot of their data, but all the history behind it as well, from one system to another. This is an extremely difficult problem to solve that involves deducing changesets in the absence of atomicity, and translating between the systems' completely orthogonal branching policies, among other complications. Still, there are a handful of tools claiming to at least partially support the ability to convert existing CVS repositories into Subversion ones.

One such tool is cvs2svn (http://cvs2svn.tigris.org/), a Python script originally created by members of Subversion's own development community. Others include Chia-liang Kao's Subversion converter plugin to the VCP tool (http://svn.clkao.org/revml/branches/svn-perl/) and Lev Serebryakov's RefineCVS (http://lev.serebryakov.spb.ru/refinecvs/). These tools have various levels of completeness, and may make entirely different decisions about how to handle your CVS repository history. Whichever tool you decide to use, be sure to perform as much verification as you can stand on the conversion results—after all, you've worked hard to build that history!

For an updated collection of links to known converter tools, visit the Links page of the Subversion website (http://subversion.tigris.org/project_links.html).

261