If you want to copy files from another project in the same repository
(like omake), you will need to convince subversion that they are actually
the same.

Here is an example.

svn switch --relocate svn://svn.metaprl.org/libmojave svn+ssh://svn.metaprl.org/svnroot/mojave/libmojave

You should commit immediately if possible, because an "svn update" will revert
back to using the old svn://... link.