Open a complete chain of Daf repositories by tracing back through the base_daf_repository property.
Each repository in a chain contains a scalar property called base_daf_repository which identifies
its parent repository (if any).
Details
If mode is "r+", only the first (leaf) repository is opened in write mode.
The base_daf_repository path is relative to the directory containing the child repository.
See the Julia documentation for details.