#!/bin/bash
set -euE

is_int() {
	local re='^[0-9]+$'
	[[ $1 =~ $re ]]
}

errusage() {
	if [[ $# != 0 ]]; then
		echo >&2 "${0##*/}: error: $*"
	fi
	echo >&2 "Usage: ${0##*/} [REMOTE] PR_NUMS..."
	return 2
}

main() {
	if [[ $# == 0 ]]; then
		errusage 'require 1 or more PR numbers'
	fi
	local remote=origin
	if ! is_int "$1"; then
		remote=$1
		shift
		if [[ $# == 0 ]]; then
			errusage 'require 1 or more PR numbers'
		fi
	fi
	local refspecs=()
	for pr in "$@"; do
		if ! is_int "$pr"; then
			errusage "not a number: ${pr@Q}"
		fi
		refspecs+=(
			"refs/pull/${pr}/head:refs/pull/${pr}/head"
			#"refs/pull/${pr}/merge:refs/pull/${pr}/merge"
                )
	done
	git fetch --force "$remote" "${refspecs[@]}"
}

main "$@"