Add rename/mv command.
This is the logical equivalent of copy and remove, and is in fact
implemented as such. It doesn't use the remove command directly.
abort: repository a/.hg not found!
255
requesting all changes
abort: error: Connection refused
255
abort: repository a/.hg not found!
255
abort: destination '../a' already exists
1
abort: repository a/.hg not found!
255
abort: destination 'q' already exists