#!/bin/sh

# Generic function to print an error message and bail out.
die ()
{
    echo $1 > /dev/stderr
    exit 1
}

# Print usage
usage ()
{
    cat <<EOF
$0 -- Generate .patch files for a RPM package from a git repository

Usage:
  $0 <REPOSITORY> [<COMMIT_OR_TAG>]

<REPOSITORY> is the directory where the rebase was performed.

<COMMIT_OR_TAG> is the commit or tag against which the rebase was
performed.  It is optional, and if not provided "origin/master" will
be used.  This script will then use 'git merge-base' to find the most
recent common ancestor between HEAD and COMMIT_OR_TAG.

Options are:

  -h: Print this message
EOF
    exit 0
}

test -f gdb.spec || die "This script needs to run from the same directory as gdb.spec."

test -z $1 && die "You need to specify the repository."
test "$1" = "-h" && usage

commit_or_tag="origin/master"
if test ! -z "$2" ; then
    commit_or_tag="$2"
fi

test -d $1 || die "$1 is not a directory."

# Remove all the current patches
for f in `cat _patch_order` ; do
    git rm -f $f
done

cd $1
idx=1
common_ancestor=`git merge-base HEAD $commit_or_tag`

test -z "$common_ancestor" && die "Could not find common ancestor between HEAD and $commit_or_tag."

temp_PATCH_file=/tmp/_gdb.spec.Patch.include
temp_patch_file=/tmp/_gdb.spec.patch.include
temp_patch_order_file=/tmp/_patch_order

rm -f $temp_PATCH_file $temp_patch_file $temp_patch_order_file

for c in `git rev-list --reverse ${common_ancestor}..HEAD` ; do
    fname=`git log -1 --pretty='format:%b' $c | sed -n 's/^FileName: \(.*\)$/\1/p'`
    test -z $fname && die "Could not determine FileName of commit $c."
    git format-patch --keep -1 --stdout $c > ../$fname
    (cd .. && git add $fname)

    cat >> $temp_PATCH_file <<EOF
`git log -1 --pretty='format:%b' $c | sed -n 's/^;;/#/p'`
EOF
    printf "Patch%03d: %s\n\n" $idx $fname >> $temp_PATCH_file
    printf "%%patch%03d -p1\n" $idx >> $temp_patch_file
    echo $fname >> $temp_patch_order_file
    idx=`expr $idx + 1`
done

cd ..
mv $temp_PATCH_file _gdb.spec.Patch.include
mv $temp_patch_file _gdb.spec.patch.include
mv $temp_patch_order_file _patch_order
echo "$common_ancestor" > _git_upstream_commit