We ended up with multiple projects needing access to the same set of internal modules. Rather than keep multiple copies of the same code in different Subversion repositories, it made sense to link the code in by way of the svn:externals property.
This took a few attempts to get right. The working propset line is below (remember to be in the directory you want to place the local directory first!):
svn propset svn:externals 'local_modules -r87 svn://subversion.hub.server/remote_repository/trunk/remote_modules' . svn update svn commit -m "Added svn:externals link to remote_modules, revision 87."
Some important notes:
- SPECIFY A REVISION NUMBER: This keeps the version of the modules in your local repository stable. They will not automatically update when a developer is fiddling around with the remote repository. Thus, things stay nicely consistent, and bringing in an updated set of modules is under your control (just update the property when ready).
- DO NOT CREATE THE LOCAL DIRECTORY FIRST: Subversion will create it for you. If it is already there, you will get lock errors. If for some reason the local directory is versioned, then you will need to delete it from Subversion first.
- LOOK AT THE QUOTES: Look at where the quote characters are. This is important. Ditto for the full stop at the end!