#!/bin/bash
#
# Author: Dave Hansen <dave@eatbacon.net> 
# xpatch: a 'patch' replacement so you can turn .src.rpms
#         into git trees.
#
####################################################
# 
#                    Why?
#
# Why do I want to do this?  I don't run RHEL, Fedora,
# SLES, or openSUSE so  I don't have rpm around all the
# time.  Novell and Redhat do not exactly make it easy
# to find their enterprise kernels, and there are a
# *LOT* of old versions.  It isn't always easy to get
# access to these, even though my company has copies
# laying around in lots of places.
#
# I often get a customer bug report saying, "I'm running
# XYZ distro kernel".  I never have source handy for
# those kernels.  If there was a git tree for all of
# them, I bet I could find and fix distro bugs much
# faster.
#
####################################################
#
#                   How?
#
# If this file is called xpatch, then doing this will
# get it in your path:
# 
#	mkdir $HOME/bin
# 	PATH=$HOME/bin:$PATH
# 	cp xpatch ~/bin/patch
# 	chmod 755 ~/bin/patch
#
# This is how I run this script after setting PATH:
#
# 	rpm -Uvh kernel-1.2.4.2.src.rpm
# 	cd /usr/src/packages/SPEC
# 	rpmbuild -bc kernel-default.spec
#
# After RPM finishes, I have a git tree with history.
#
# If the RPM is based off of 2.6.27.33, then the
# resulting git tree will be based off of the -stable
# git tree's v2.6.27.33.
# 
# Each distro-applied patch gets entered as its own
# commit.  Most of them have nice author and SOB lines,
# as well as dates.  This means I can use git-blame to
# find culprits who introduce distro bugs.


set -e
function ver
{
	eval `cat Makefile | head -4  | perl -pe 's/ //g'`
	echo $VERSION.$PATCHLEVEL.$SUBLEVEL$EXTRAVERSION
}
function gitaddnew
{
	git ls-files -o --exclude-standard | xargs --no-run-if-empty git add 
}
VER=$(ver)
if ! [ -d .git ]; then
	echo first patch run?? >&2
	echo ver: $VER
	#git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-2.6-stable.git linux.git
	echo copying git dir...
	cp -r /home/dave/linux/.git/ ./
	git describe
	echo adding...
	gitaddnew
	echo diffing...
	if ! git diff v$VER | head -100 | diffstat | grep '^ 0 files changed'; then
		echo unable to find starting git revision
		exit 1
	fi
	git reset v$(ver)
	echo diffstat:
	git diff v$VER | head -100 | diffstat
	git describe
	echo sleeping...
	sleep 10
	VER=""
fi
PATCHNEXT=false
PATCH="$(readlink /proc/self/fd/0)"
for arg in "$@"; do
	if $PATCHNEXT; then
		PATCH="$arg"	
		break;
	fi
	if [ "$arg" == "-i" ]; then
		PATCHNEXT=true
	fi;
done
echo PATCH: "'$PATCH'"
{ 
	echo my stdin is from \"`readlink /proc/self/fd/0`\"
	echo PATCH: "'$PATCH'"
	echo args: "$@"
}	>> ~/logs/patch.log
/usr/bin/patch "$@"

# This is magic.  It assumes that any patch changing the
# kernel version is taking us to a new mainline release,
# and it triggers us to try and merge with that git
# commit from Linus's (or the -stable) tree.
#
# This might be better done by comparing the patches
# themselves with the kernel.org patches, but this seems
# to work OK for now.

RET=$?
VER2=$(ver)
if [ "$VER" == "$VER2" ]; then
	echo version did not change.  What happened?
	exit 2
	exit $RET
fi
echo changing ver from $VER to $VER2
VER=$VER2
git describe
gitaddnew
git diff v$(ver) | diffstat | grep '^ 0 files changed' && git reset v$(ver)
git describe
exit $RET