Check for parent/mod as well as parent.mod in findext.
Debian/Ubuntu ship a system-wide hgrc that loads extensions using
the syntax hgext/extension=, rather than hgext.extension=. Although
the extensions work correctly, hg help <extension> doesn't
understand this form without this patch.
Content-type: text/html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<link rel="icon" href="?static=hgicon.png" type="image/png">
<meta name="robots" content="index, nofollow" />
<link rel="stylesheet" href="?static=style.css" type="text/css" />