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.
#!/bin/sh
mkdir t
cd t
hg init
echo "invalid" > .hg/hgrc
hg status 2>&1 |sed -e "s:/.*\(/t/.*\):...\1:"