Mercurial's documentation is currently kept in ASCIIDOC format, which
is a simple plain text format that's easy to read and edit. It's also
convertible to a variety of other formats including standard UNIX man
page format and HTML.

To do this, you'll need to install ASCIIDOC:

 http://www.methods.co.nz/asciidoc/

To generate the man page:

 asciidoc -d manpage -b docbook hg.1.txt
 xmlto man hg.1.xml

To display:

 groff -mandoc -Tascii hg.1 | more

To create the html page (without stylesheets):

 asciidoc -b html4 hg.1.txt

(older asciidoc may want html instead of html4 above)