repofilecache: define a 'join' method We are about to turn the 'join' method of the base class Abstract, so we need on to be defined in the localrepo. The ultimate goal here is to be able to stop relying for the 'localrepo' class to have a 'join' methods (there is above one hundred methods on 'localrepo'. This change make te 'repo' file cache have its own code so that we can prepare this change to the repostory class. explicite join