share: move the implementation of 'unshare' to the 'hg' module
This will be used to setup unsharing subrepos. Usually cmdutil is used for
this purpose. But the implementation needs hg.copystore(), and the hg module
already imports cmdutil.
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
http://docutils.sourceforge.net/
Use the Makefile in this directory to generate the man and HTML pages.