svn:externals "http://svn.3rdapp.com/project/subdir/subdir/ lib/mydir/subdir"
SVN allows developers to include sub-directories of 3rd party libraries into sub-directories of their own repo.
I'd like to include only a sub-directory of the 3rd party lib into my project, likely as a subtree which can be edited and new upstream changes merged with my edits.
Specifically https://github.com/openid/php-openid/tree/master/Auth included into Vendor/Auth without any of the files or history from the other directories.