Change asciidoc backend to more recent name. The latest asciidoc doesn't have an 'html' backend. 'html' was last valid with version 6 ( 2005-1-28). Current options are xhtml11, or html4, with xhtml11 by default.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test -d "0 0"
hg history
hg manifest
hg cat a
hg verify