The doctrine:build-* tasks all create a "base/" directory with generated content. Usually it is a bad practice to add generated files to the SVN repositorys (see the KDE Policy[1] for example), because the changes in generated files are completely irrelevant (they can be regenerated anyway).
I usually add all "base" directories in "form/doctrine", "filter/doctrine" and "model/doctrine" as well as in the generated plugin directories to svn:ignore. This is a very tedious task though that one can easily forget. Thus I suggest to introspect whether the symfony project is in an SVN working copy and, if yes, to automatically add these directories to svn:ignore.
You can easily find out whether a project is a working copy by verifying whether a ".svn" directory is available in the project root.
[1] http://techbase.kde.org/Policies/SVN_Commit_Policy#Don.27t_add_generated_files_to_the_repository