#!/bin/bash

# Copyright 2017 The Kubernetes Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


# overall flow
# 1. fetch the current level of k8s.io/kubernetes
# 2. check out the k8s.io/kubernetes HEAD into a separate branch
# 3. rewrite the history on that branch to *only* include staging/src/k8s.io/apimachinery
# 4. locate all commits between the last time we sync'ed and now
# 5. switch back to the starting branch
# 6. for each commit, cherry-pick it (which will keep authorship) into current branch
# 7. update metadata files indicating which commits we've sync'ed to

set -e

dir=$(mktemp -d "${TMPDIR:-/tmp/}$(basename 0).XXXXXXXXXXXX")

git remote add upstream-kube git@github.com:kubernetes/kubernetes.git  || true
git fetch upstream-kube

currBranch=$(git rev-parse --abbrev-ref HEAD)
previousKubeSHA=$(cat kubernetes-sha)
previousBranchSHA=$(cat filter-branch-sha)

git branch -D kube-sync || true
git checkout upstream-kube/master -b kube-sync
git reset --hard upstream-kube/master
newKubeSHA=$(git log --oneline --format='%H' kube-sync -1)

# this command rewrite git history to *only* include staging/src/k8s.io/apimachinery
git filter-branch -f --subdirectory-filter staging/src/k8s.io/apimachinery HEAD

newBranchSHA=$(git log --oneline --format='%H' kube-sync -1)
git log --no-merges --format='%H' --reverse ${previousBranchSHA}..HEAD > ${dir}/commits

git checkout ${currBranch}

while read commitSHA; do
	echo "working ${commitSHA}"
	git cherry-pick ${commitSHA}
done <${dir}/commits

# track the k8s.io/kubernetes commit SHA so we can always determine which level of kube this repo matches
# track the filtered branch commit SHA so that we can determine which commits need to be picked
echo ${newKubeSHA} > kubernetes-sha
echo ${newBranchSHA} > filter-branch-sha
git commit -m "sync(k8s.io/kubernetes): ${newKubeSHA}" -- kubernetes-sha filter-branch-sha