util: Add script to update release branch from master

Currently this script is specific to the fingerprint release branch
process, but can be easily generalized to other ECs. See
http://go/cros-fingerprint-firmware-branching-and-signing.

BRANCH=none
BUG=none
TEST=./util/update_release_branch.sh

Change-Id: I66087190754c789387a6537b69a026c81f93ead0
Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2088602
Reviewed-by: Craig Hesling <hesling@chromium.org>

util/update_release_branch.sh

@@ -0,0 +1,95 @@
+#!/bin/bash
+
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Tool to merge master branch into a release branch. Currently specific to the
+# fingerprint sensor, but can easily be generalized. See
+# http://go/cros-fingerprint-firmware-branching-and-signing.
+
+. /usr/share/misc/shflags
+
+DEFINE_string 'board' "bloonchipper" 'EC board (FPMCU) to update' 'b'
+
+# Process commandline flags.
+FLAGS "${@}" || exit 1
+eval set -- "${FLAGS_ARGV}"
+
+set -e
+
+# Dereference symlinks so "git log" works as expected.
+readonly BOARD_DIR="$(realpath --relative-to=. "board/${FLAGS_board}")"
+readonly RELEVANT_PATHS=(
+  "${BOARD_DIR}"
+  common/fpsensor
+  docs/fingerprint
+  driver/fingerprint
+  util/getversion.sh
+)
+readonly RELEASE_BRANCH="firmware-fpmcu-${FLAGS_board}-release"
+
+get_relevant_commits_cmd() {
+  local head="${1}"
+  local merge_head="${2}"
+  local format="${3}"
+
+  local relevant_commits_cmd="git log ${format} ${head}..${merge_head}"
+  relevant_commits_cmd+=" -- ${RELEVANT_PATHS[*]}"
+  echo "${relevant_commits_cmd}"
+}
+
+git_commit_msg() {
+  local branch="${1}"
+  local head="${2}"
+  local merge_head="${3}"
+
+  local relevant_commits_cmd
+  local relevant_commits
+  local relevant_bugs_cmd
+  local relevant_bugs
+
+  relevant_commits_cmd="$(get_relevant_commits_cmd "${head}" \
+    "${merge_head}" "--oneline")"
+  relevant_commits="$(${relevant_commits_cmd})"
+  relevant_bugs_cmd="$(get_relevant_commits_cmd "${head}" \
+    "${merge_head}" "")"
+  relevant_bugs="$(${relevant_bugs_cmd} | \
+    pcregrep -o1 'BUG=(.*)' | pcregrep -v none | \
+    tr ' ' '\n' | tr ',' '\n' | \
+    sort | uniq | xargs)"
+
+  cat <<HEREDOC
+Merge remote-tracking branch 'm/master' into ${branch}
+
+Relevant changes:
+
+${relevant_commits_cmd}
+
+${relevant_commits}
+
+BRANCH=none
+BUG=${relevant_bugs}
+TEST=test_that --board <board> <IP> suite:fingerprint
+HEREDOC
+}
+
+merge_master() {
+  git remote update
+  git checkout -B "${RELEASE_BRANCH}" "cros/${RELEASE_BRANCH}"
+  git merge --no-ff --no-commit m/master
+
+  local branch
+  local head
+  local merge_head
+
+  branch="$(git rev-parse --abbrev-ref HEAD)"
+  head="$(git rev-parse --short HEAD)"
+  merge_head="$(git rev-parse --short MERGE_HEAD)"
+
+  git commit --signoff -m "$(git_commit_msg "${branch}" \
+    "${head}" "${merge_head}")"
+  git commit --amend
+}
+
+merge_master