The Thunar project uses the subversion concurrent versions system (aka SVN) to manage documents and files used in the development of the file manager.
Currently, there are three ways to access the repository, either using the WebSVN interface, anonymous HTTP+DAV access, or for the developers, using HTTPS+DAV.
Anonymous web access to the SVN repository is provided through WebSVN which allows you to browse the repository using a Web Browser and download files from the repository without the need to have an account.
Anonymous SVN can be checked out by using the subversion cli “svn” as follows:
svn co http://svn.xfce.org/svn/xfce/thunar/trunk/ thunar
Developers can use their https accounts to access the repository. For example, to checkout the trunk, you would use the command
svn co https://username@xfce.org/svn/xfce/thunar/trunk/ thunar
replacing username with your account name.
Make sure you read the subversion handbook before starting to use SVN as a developer.