ubuntu-dev-tools/what-patch

#!/bin/bash
# Copyright 2006-2007 (C) Kees Cook <kees@ubuntu.com>
# Modified by Siegfried-A. Gevatter <siggi.gevatter@gmail.com>
# License: GPLv2

if [[ -d debian ]]; then
    cd . # pass
elif [[ -d ../debian ]]; then
    cd ..
elif [[ -d ../patches ]]; then
    cd ../.. 
else
    echo "Can't find debian/rules."; exit
fi

for filename in $(echo "debian/rules"; grep ^include debian/rules | fgrep -v '$(' | awk '{print $2}')
do
    fgrep -q patchsys.mk "$filename" && { echo "cdbs"; exit; }
    fgrep -q quilt "$filename" && { echo "quilt"; exit; }
    fgrep -q dbs-build.mk "$filename" && { echo "dbs"; exit; }
    fgrep -q dpatch "$filename" && { echo "dpatch"; exit; }
    fgrep -q '*.diff' "$filename" && { echo "diff splash"; exit; }
done
[ -d debian/patches ] || { echo "patchless?"; exit; }
echo "unknown patch system"