my-local-dir/$ svn cp trunk tags/3.7.1
> A tags/3.7.1

my-local-dir/$ svn ci -m "tagging version 3.7.1"
> Adding         tags/3.7.1
> Adding         tags/3.7.1/my-plugin Recommended Reading.php
> Adding         tags/3.7.1/readme.txt
> Committed revision 11328.

# Erledigt!