#!/bin/bash

set -euo pipefail

if [ $# -lt 1 ] || [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
  echo "Usage: $0 TAG"
  echo "Rebases the free-standing git tag <TAG> on the current branch"
  echo "(make sure you don't have any uncommited local changes)"
  echo "E.g., after a Jenkins build 'alpha-9999.99.99-mytest' was started based on"
  echo "the scripts branch 'mybranch' and you have new changes on the branch,"
  echo "check out your branch and run"
  echo "  $0 alpha-9999.99.99-mytest"
  echo
  echo "This is required when testing 'scripts' changes with Jenkins and a leaf job fails,"
  echo "so that instead of restarting the whole build from the 'packages' job, you can"
  echo "restart the leaf job after retagging. Note: Just starting a leaf job with your"
  echo "branch as reference is not valid because it would overwrite the nightly build"
  echo "artifacts!"
  exit 1
fi

TAG="$1"
BRANCH=$(git rev-parse --abbrev-ref HEAD)
git fetch --force --tags origin
BUILD_PATCH=$(git format-patch --output=/dev/stdout "${TAG}~1..${TAG}")
git checkout --recurse-submodules "${TAG}"
git reset --hard "${BRANCH}"
echo "${BUILD_PATCH}" | git am -3 || {
  git checkout "${TAG}" -- sdk_container/.repo/manifests/version.txt
  git add sdk_container/.repo/manifests/version.txt
  git am --continue
  # This does not handle submodule conflicts: It should use the one
  # from the TAG (similar to version.txt) unless an explicit new
  # reference was specified
} || { echo "Failed to resolve conflict, continue manually" >&2 ; exit 1 ; }
git tag -d "${TAG}"
git tag "${TAG}"
git push --force origin "${TAG}"