add(master_release): Add script for updating master's version.txt

This is intended to be called after branch_release and all official
builds from that new branch are complete. Then updating master's
version.txt will switch things to start using that new release as the
source for binary packages.

Complete documentation for this whole process coming soon. :)

master_release

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+# Copyright (c) 2013 The CoreOS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+SCRIPT_ROOT=$(dirname $(readlink -f "$0"))
+. "${SCRIPT_ROOT}/common.sh" || exit 1
+
+COREOS_EPOCH=1372636800  # Mon Jul  1 00:00:00 UTC 2013
+TODAYS_VERSION=$(( (`date +%s` - ${COREOS_EPOCH}) / 86400 ))
+TODAYS_VERSION=$(printf "%04d" "${TODAYS_VERSION}")
+
+DEFINE_string master "master" "Manifest master branch to update."
+DEFINE_string branch "build-${TODAYS_VERSION}" \
+    "Manifest branch, tag, or other ref to get version from."
+DEFINE_boolean push ${FLAGS_FALSE} "Push to public manifest repository."
+DEFINE_string remote "origin" "Remote name or URL to push to."
+
+# Parse flags
+FLAGS "$@" || exit 1
+eval set -- "${FLAGS_ARGV}"
+switch_to_strict_mode
+
+info "Running repo init -b ${FLAGS_master}"
+repo init -b "${FLAGS_master}"
+
+info "Updating version.txt from ${FLAGS_branch}"
+cd "${GCLIENT_ROOT}/.repo/manifests"
+git checkout "${FLAGS_branch}" version.txt
+git add version.txt
+git commit -m "bump(version): Update version from ${FLAGS_branch}"
+
+if [[ ${FLAGS_push} -eq ${FLAGS_TRUE} ]]; then
+    info "Pushing to ${FLAGS_remote} ${FLAGS_master}"
+    git push "${FLAGS_remote}" "HEAD:refs/heads/${FLAGS_master}"
+fi