#!/bin/bash
# Copyright 2021 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.
#
# Script to create a commit to merge cros/main into cros/chromeos with a useful
# commit message.
#
# Basic usage to upload a merge to gerrit:
#
#   $ repo start uprev .
#   $ ./tools/chromeos/create_merge
#   $ git push cros HEAD:refs/for/chromeos
#
# To merge with a specific commit, use: ./tools/chromeos/create_merge $SHA

set -e

if [ "$1" == "--dry-run-only" ]; then
    DRY_RUN_ONLY=true
    shift
fi

LOCAL_BRANCH=$(git branch --show-current)
REMOTE_NAME=$(git config "branch.${LOCAL_BRANCH}.remote")
URL=$(git remote get-url "${REMOTE_NAME}")

DEFAULT_TARGET="${REMOTE_NAME}/main"
MERGE_TARGET="${1:-${DEFAULT_TARGET}}"

commit_list() {
    git log --oneline --decorate=no --no-color "HEAD..${MERGE_TARGET}"
}

prerequisites() {
    if [[ -e "${LOCAL_BRANCH}" ]] ||
        [[ -e "${REMOTE_NAME}" ]] ||
        [[ -e "${URL}" ]]; then
        echo "This script requires the local repository to be on" \
            "a tracking branch."
        exit 1
    fi

    if [[ -n $(git status -s) ]]; then
        echo "Working directory is not clean:"
        git status -s
        exit 1
    fi

    if [[ -z "$(commit_list)" ]]; then
        echo "Nothing to merge."
        exit 0
    fi
}

cq_depends() {
    git log --no-color "HEAD..${MERGE_TARGET}" --pretty=email |
        grep ^Cq-Depend: |
        sort -u
}

bug_references() {
    git log --no-color "HEAD..${MERGE_TARGET}" --pretty=email |
        grep ^BUG= |
        grep -vi ^BUG=none |
        sort -u
}

merge_message() {
    local old=$(git rev-parse HEAD)
    local new=$(git rev-parse "${MERGE_TARGET}")
    local count=$(commit_list | wc -l)

    local notes="$(date +%F)"
    if [[ -n "$(cq_depends)" ]]; then
        notes="${notes}, cq-depend"
    fi

    if [ "${DRY_RUN_ONLY}" = true ]; then
        echo "Merge dry run (${notes})"
    else
        echo "Merge ${count} commits from ${MERGE_TARGET} (${notes})"
    fi
    echo ""
    commit_list
    echo ""
    echo "${URL}/+log/${old}..${new}"
    echo ""
    if [ "${DRY_RUN_ONLY}" != true ]; then
        bug_references
    fi
    echo "TEST=CQ"
    echo ""
    cq_depends
    if [ "${DRY_RUN_ONLY}" = true ]; then
        echo "Commit: false"
    fi
}

main() {
    prerequisites
    git merge -X theirs --no-ff "${MERGE_TARGET}" -m "$(merge_message)"
    git --no-pager log -n 1
}

main