The `svn2cl' command includes pathnames for files which aren't under the current directory. Here is a patch to stop it doing that. I don't speak XSL, so I made the change in AWK. I notice that the author is aware of this shortcoming already:
$ grep TODO /etc/svn2cl/svn2cl.xsl
<!-- TODO: do not print strings that do not begin with \
This patch reduces the size of the Changelog in synfig-studio/src/synfigapp/ from 102KB to 22KB.