add script for creating release tarballs

In the future we'll change how our releases look like. This script
is a preliminary outline.

release.sh

@@ -0,0 +1,109 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2018, Martin Kepplinger <martink@posteo.de>
+#
+# Script to build release-archives with. This requires a checkout from git.
+# WARNING: This script is very dangerous! It may delete any untracked files.
+set -e
+have_version=0
+have_image=0
+
+usage()
+{
+        echo "Usage: $0 -v version -i release_image"
+}
+
+args=$(getopt -o v:i: -- "$@")
+if [ $? -ne 0 ] ; then
+        usage
+        exit 1
+fi
+eval set -- "$args"
+while [ $# -gt 0 ]
+do
+        case "$1" in
+	-i)
+		RELEASE_IMAGE=$2
+		have_image=1
+		shift
+		;;
+        -v)
+                version=$2
+                have_version=1
+                shift
+                ;;
+        --)
+                shift
+                break
+                ;;
+        *)
+                echo "Invalid option: $1"
+                usage
+                exit 1
+                ;;
+        esac
+        shift
+done
+
+# Do we have a desired version number?
+if [ "$have_version" -gt 0 ] ; then
+       echo "trying to build version $version"
+else
+       echo "please specify a version"
+       usage
+       exit 1
+fi
+
+# Version number sanity check
+if grep ${version} NEWS
+then
+       echo "configurations seems ok"
+else
+       echo "please check the NEWS file"
+       exit 1
+fi
+
+# Check that we are on master
+branch=$(git rev-parse --abbrev-ref HEAD)
+echo "we are on branch $branch"
+
+if [ ! "${branch}" = "master" ] ; then
+	echo "you don't seem to be on the master branch"
+	exit 1
+fi
+
+if git diff-index --quiet HEAD --; then
+	# no changes
+	echo "there are no uncommitted changes (version bump)"
+	exit 1
+fi
+echo "======================================================"
+echo "    are you fine with the following version bump?"
+echo "======================================================"
+git diff
+echo "======================================================"
+read -p "           Press enter to continue"
+echo "======================================================"
+
+filesize=$(wc -c <"${RELEASE_IMAGE}")
+reference_filesize=4194304
+if [ ! $filesize -eq "$reference_filesize" ] ; then
+	echo "filesize of release image is wrong"
+	exit 1
+fi
+
+tar -cJf coreboot-x230-${version}.tar.xz \
+	README.md \
+	NEWS \
+	LICENSE* \
+	prepare_internal_flashing.sh \
+	${RELEASE_IMAGE}
+
+git clean -d -f
+
+git commit -a -m "update to ${version}"
+git tag -s ${version} -m "coreboot-x230 ${version}"
+
+sha256sum coreboot-x230-${version}.tar.xz > coreboot-x230-${version}.tar.xz.sha256
+sha1sum coreboot-x230-${version}.tar.xz > coreboot-x230-${version}.tar.xz.sha512
+gpg -b -a coreboot-x230-${version}.tar.xz