External rails plugin resources (and how to get rid of them)

Since it seems state of the art to keep plugins as external resources I tried myself to install them via script/plugin -x URL. 

Maybe I am missing some points here, of course it has some advantages, but in reality this has some big flaws. I would like to keep control over my sourcecode and dont want to deploy on production suddenly realizing there is a new version of a plugin out there. 

These external biests are really hard to handle with svn, like merging. Or imagine you need to make changes to these resouces.
Sad but true I found no documentation how to remove these plugins. It cost me some effort to find out since I am no svn guru. But its pretty easy. Just call

svn propedit svn:externals vendor/plugins. 

If you get a message that no SVN_EDITOR is defined you have to do that:

export SVN_EDITOR=mate

Delete all the external resource entries (file should be blank afterwards) and commit the vendor/plugins directory. Maybe you need a clean checkout before to do this properly.