checkheads: take future obsoleted heads into account
If we push some successors they will likely create a new head on
remote. However as the obsoleted head will disappear after the push we
are not really increasing the number of heads.
There is several case which will lead to extra being actually pushed. But this
first changeset aims to be simple. See the inline comment for details.
Without this change, you need to push --force every time you want to
push a newer version which is very error prone.
The remote side still display +n heads on unbundle because it does not have the
obsolete marker at unbundle time.
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.