Is it a horrible hack to have an empty SVN dir, just to pull externals together?

Regarding having several libraries each wit开发者_StackOverflow中文版h their own tags/trunk/branches structure... and you want to get trunk from each into a working-directory.

Easy to setup, I think. An empty SVN dir "libs", using svn:external on each library you want.

But this sounds rather ugly, like a hack to avoid using a proper build script. Is it ever used, and is it a useful trick or a dirty hack that should be avoided?

It is hacky - svn:externals nearly always. Be sure to always use explicit revisions (preferably tags (which should be atomic anyway), not a branch or the trunk) in your external definitions. You will quickly lose the ability to rebuild in older sections of the tree if you aren't diligent.

You may want to look into some kind of dependency management - building and publishing the libraries to a repository and having the application(s) that depend on them pull them down in their build. The Java world has this down with maven or ant/ivy. It may be worth your while to explore what your platform/tooling has available in this area.