subrepo: subrepo isolation, pass baseui when cloning a new subrepo (issue2904) Create the repo with baseui because it should only get the global configuration. After this patch issue2904 is finally fixed.

subrepo: more isolation, only use ui for hg.peer when there is no repo ui contains repo specific configuration, so do not use it when there is a repo. But pass it to hg.peer when there is no repo. Then it only contains global configuration.

peer: subrepo isolation, pass repo instead of repo.ui to hg.peer Do not pass ui because it contains the configuration of the repo. It is the same object as repo.ui. When a repo is passed to hg.peer, the global configuration is read from repo.baseui.