At some point all files in my working copy got marked with \"S\" symbol as shown below:
$ svn st M S AclController.php S InstallationController.php
A simple solution to get rid of the 'S' when you issue
svn status
is to just go to the dir that is marked with 'S' and delete the hidden .svn directory:
rm -rf .svn
Afterwards the sources show up marked with '?' and you could easily add them freshly:
svn add path/to/resource