hg.py: add islocal() and defaultdest() functions, refactor
islocal tells if a repo or url is local.
defaultdest returns default path for clone if explicit path not given.
clone can now take repo or url as source
abort: repository a not found!
255
abort: error: Connection refused
255
abort: repository a not found!
255
abort: destination '../a' already exists
255
abort: repository a not found!
255
abort: destination 'q' already exists