Always try to open the repository if -R/--repository is specified.
This makes 'hg -R something_unknown command' consistently fail for
all commands, not only for those who need a repository.
abort: repository a not found!
255
requesting all changes
abort: error: Connection refused
255
abort: repository a not found!
255
abort: destination '../a' already exists
1
abort: repository a not found!
255
abort: destination 'q' already exists