Please let me know what is the Subversion/SVN URL of the docbook-xsl-ns and docbook-xsl stylesheets that can be found here: http://docbook.sourceforge.net/snapshot/ . I want to do an "svn checkout"/"svn co" command and update it using "svn update"/"svn up".
http://snapshots.docbook.org/ hosts snapshot releases built from sources in the DocBook Subversion repository (the http://docbook.sourceforge.net/snapshot/ location is obsolete).
The root of the repository is at https://docbook.svn.sourceforge.net/svnroot/docbook. You can check out anything you want from there. The core source module for stylesheet development is "xsl". To check it out (trunk branch), execute
svn co https://docbook.svn.sourceforge.net/svnroot/docbook/trunk/xsl
You can do a build of docbook-xsl/docbook-xsl-ns yourself. This takes some preparation. For more information, see: