Embedding a working copy in a vendor branch

Hi,

Over the years I have been using (T)SVN for lots of different
projects, but this is something new. I want to start my own
development (private repository) of some components/plugins for
Joomla!. However, the folder structure of Joomla! is such that the
files for these components/plugins must be spread across the source
tree of Joomla! itself.

So, on the one hand I have a need for a working copy (develop/test
setup) that contains the Joomla! source as an svn:external, but that
has regular folders/files for my personal additions. In a way I need
my working copy to reside inside a vendor branch.

Are there some other (T)SVN users with experience who could give some
hints on how to proceed?

Is is best to create a separate WC and add some 'build' step to copy
the code into the Joomla! WC (or export) prior to testing (a bit of a
PITA compared to just saving the files and hitting f5 in the browser).

-- 
Regards,
Jean-Marc
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