localrepo: prevent to copy repo local config, copy baseui instead
Copying a repos local configuration to another repo is a bad idea because the
2nd repo gets the configuration of the first. Prevent this by really calling
repo.baseui.copy when repo.ui.copy is called.
This requires some changes in commandserver which needs to clone repo.ui for
rejecting temporary changes.
This patch has its roots back in the topic "repo isolation" around f0564402d059
and was suggested by mpm.