die()
{
  printf "E: $@\n" >&2
  exit 1
}

tg_ds_resolve_commit()
{
  git rev-parse --verify $1 2>/dev/null
}

. ${0%/*}/tg-datastore-pcommits.inc

tg_ds_get_value()
{
  local name; name="${1:-}"
  local commit; commit="${2:-HEAD}"

  [ -z "$1" ] && die 'tg_ds_get_value: missing first argument (name)'
  tg_ds_resolve_commit $commit >/dev/null || die "tg_ds_get_value: invalid commit: $commit"

  local data; data=$(tg_ds_list_data "$commit") || return 1
  printf "$data\n" | sed -rne "s,^${name}: *,,p"
}

tg_ds_find_value()
{
  local name; name="${1:-}"
  local commit; commit="${2:-HEAD}"

  [ -z "$1" ] && die 'tg_ds_find_value: missing first argument (name)'
  ref=$(tg_ds_resolve_commit $commit) || die "tg_ds_find_value: invalid commit: $commit"

  while :; do
    if [ "$name" = commitref ]; then
      tg_ds_list_data "$commit" >/dev/null && printf "$ref\n" && return 0
    else
      tg_ds_get_value "$name" $commit && return 0
    fi
    commit="${commit}^"
    ref=$(tg_ds_resolve_commit "${commit}") || break
  done

  return 1
}