localrepo: refactor prepush logic
Simplifies the prepush check logic and makes it a lot more direct and
comprehensible. Instead of comparing the total local vs. remote head count, it
compares the number of new vs. removed heads.
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.