We need to unroll the dependency loop in order to deprecate the CatalogClient class:

library dependency cycle detected: build/opt/mongo/s/libgrid.so => build/opt/mongo/s/catalog/libsharding_catalog_client_impl.so => build/opt/mongo/s/client/libsharding_client.so => build/opt/mongo/s/libgrid.so

The criteria to test that the dependency loop is eliminated is to add some dummy calls to libsharding_client from ShardRegistry, and fix all the link errors resulting from this.

Most likely it will be sufficient to move everything from grid into libsharding_client, but before mechanically doing so, try to find a proper home for every class in the grid.