#!/bin/bash
#
# rebase a set of patches, assumes the kernel has already been downloaded into
# the kpatch $CACHEDIR.Output patches go into ./${ID}-${VERSION_ID}/
#
# Example:
#
# ./rebase-patches old_dir/*.patch

CACHEDIR="${CACHEDIR:-$HOME/.kpatch}"
SRCDIR="$CACHEDIR/src"

source /etc/os-release
OUTDIR=$(pwd)/${ID}-${VERSION_ID}
mkdir -p $OUTDIR

echo "* Making backup copy of kernel sources"
rm -rf ${SRCDIR}.orig
cp -r $SRCDIR ${SRCDIR}.orig


for P in $@; do

  echo
  echo "* Patch: $(basename $P)"

  echo "** dry run..."
  patch -d $CACHEDIR --dry-run --quiet -p0 < $P
  [[ $? -ne 0 ]] && echo "*** Skipping! ***" && continue

  echo "** patching..."
  patch -d $CACHEDIR -p0 --no-backup-if-mismatch < $P

  echo "** generating new $(basename $P)..."
  NEWP=$OUTDIR/$(basename $P)
  awk '/^diff|^patch/{exit} {print $LF}' $P > $NEWP
  cd $CACHEDIR
  diff -Nupr src.orig src >> $NEWP
  cd -

  echo "** reversing patch to restore tree..."
  patch -d $CACHEDIR -p0 -R < $NEWP

done

echo "*** Removing backup copy of kernel sources"
rm -rf ${SRCDIR}.orig

echo
echo "*** Done"