typo fix in command help text
This patch fixes a few typo errors on the command help output
(I am not sure if the change on 'diff' is the best though).
+ hg clone http://localhost:20059/ copy
requesting all changes
abort: error: Connection refused
255
ls: copy: No such file or directory
+ hg clone http://localhost:20059/foo copy2
requesting all changes
abort: HTTP Error 404: File not found
255