diffstat: made test case work with POSIX sh and printf
* arithmetic expression ((...)), without $, is bashism.
* printf '\xXX' seems non-standard. '\0' is okay.
http://www.opengroup.org/onlinepubs/
009695399/utilities/printf.html
tested with bash 4.0 and dash 0.5.5.1
#!/bin/sh
echo "[extensions]" >> $HGRCPATH
echo "hgk=" >> $HGRCPATH
hg init repo
cd repo
echo a > a
hg ci -Am adda
hg debug-cat-file commit 0