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
#header#
<title>#repo|escape#: #file|escape# history</title>
<description>#file|escape# revision history</description>
#entries%filelogentry#
</channel>
</rss>