#!/bin/bash
### automerge - automatically merge the Emacs release branch to master

## Copyright (C) 2018-2022 Free Software Foundation, Inc.

## Author: Glenn Morris <rgm@gnu.org>
## Maintainer: Stefan Kangas <stefan@marxist.se>

## This file is part of GNU Emacs.

## GNU Emacs is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.

## GNU Emacs is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.

## You should have received a copy of the GNU General Public License
## along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

### Commentary:

## Automatically merge the Emacs release branch to master.
## If the merge succeeds, optionally build and test the results,
## and then push it.
## Intended usage:
## Have a dedicated git directory just for this.
## Have a cron job that calls this script with -r -p.
##
## Modifying a running shell script can have unpredictable results,
## so the paranoid will first make a copy of this script, and then run
## it with the -d option in the repository directory, in case a pull
## updates this script while it is working.

die ()                 # write error to stderr and exit
{
    [ $# -gt 0 ] && echo "$PN: $*" >&2
    exit 1
}

PN=${0##*/}                     # basename of script
PD=${0%/*}

[ "$PD" = "$0" ] && PD=.        # if PATH includes PWD

usage ()
{
    cat 1>&2 <<EOF
Usage: ${PN} [-b] [-d] [-e emacs] [-n nmin] [-p] [-r] [-t] [-- mflags]
Merge the Emacs release branch to master.
Passes any non-option args to make (eg -- -j2).
Options:
-d: no initial cd to parent of script directory
-e: Emacs executable to use for the initial merge (default $emacs)
-n: minimum number of commits to try merging (default $nmin)
-b: try to build after merging
-t: try to check after building
-p: if merge, build, check all succeed, push when finished (caution!)
-r: start by doing a hard reset (caution!) and pull
EOF
    exit 1
}


## Defaults.

emacs=emacs
nmin=10
build=
test=
push=
quiet=
reset=
nocd=

while getopts ":hbde:n:pqrt" option ; do
    case $option in
        (h) usage ;;

        (b) build=1 ;;

        (d) nocd=1 ;;

        (e) emacs=$OPTARG ;;

        (n) nmin=$OPTARG ;;

        (p) push=1 ;;

        (q) quiet=1 ;;

        (r) reset=1 ;;

        (t) test=1 ;;

        (\?) die "Bad option -$OPTARG" ;;

        (:) die "Option -$OPTARG requires an argument" ;;

        (*) die "getopts error" ;;
    esac
done
shift $(( --OPTIND ))
OPTIND=1


[ "$nocd" ] || {
    # $PD should be the admin directory
    cd $PD || die "Could not change directory to $PD"
    cd ../
}

[ -d admin ] || die "Could not locate admin directory"

[ -e .git ] || die "No .git"


## Does not work 100% because a lot of Emacs batch output comes on
## stderr (?).
[ "$quiet" ] && exec 1> /dev/null


[ "$push" ] && test=1
[ "$test" ] && build=1


if [ -x "$(command -v mktemp)" ]; then
    tempfile=$(mktemp "/tmp/$PN.XXXXXXXXXX")
else
    tempfile=/tmp/$PN.$$
fi

trap 'rm -f $tempfile 2> /dev/null' EXIT


[ -e Makefile ] && [ "$build" ] && {
    echo "Cleaning..."
    make maintainer-clean >& /dev/null
}


[ "$reset" ] && {
    echo "Resetting..."
    git reset -q --hard origin/master || die "reset error"

    echo "Pulling..."
    git pull -q --ff-only || die "pull error"
}


rev=$(git rev-parse HEAD)

[ "$(git rev-parse @{u})" = "$rev" ] || die "Local state does not match origin"


merge ()
{
    echo "Merging..."

    if $emacs --batch -Q -l ./admin/gitmerge.el \
              --eval "(setq gitmerge-minimum-missing $nmin)" -f gitmerge \
              >| "$tempfile" 2>&1; then
        echo "merged ok"
        return 0

    else
        grep -E "Nothing to merge|Number of missing commits" "$tempfile" && \
            exit 0

        cat "$tempfile" 1>&2

        die "merge error"
    fi
}


merge


## FIXME it would be better to trap this in gitmerge.
## NEWS should never be modified, only eg NEWS.26.
git diff --stat --cached origin/master | grep -q "etc/NEWS " && \
    die "etc/NEWS has been modified"


[ "$build" ] || exit 0


echo "Running autoreconf..."

autoreconf -i -I m4 2>| "$tempfile"

retval=$?

## Annoyingly, autoreconf puts the "installing `./foo' messages on stderr.
if [ "$quiet" ]; then
    grep -v 'installing `\.' "$tempfile" 1>&2
else
    cat "$tempfile" 1>&2
fi

[ $retval -ne 0 ] && die "autoreconf error"


echo "Running ./configure..."

## Minimize required packages.
./configure --without-x || die "configure error"


echo "Building..."

make "$@" || die "make error"

echo "Build finished ok"


[ "$test" ] || exit 0


echo "Testing..."

## We just want a fast pass/fail, we don't want to debug.
make "$@" check TEST_LOAD_EL=no || die "check error"

echo "Tests finished ok"


[ "$push" ] || exit 0


## In case someone else pushed while we were working.
echo "Checking for remote changes..."
git fetch || die "fetch error"

[ "$(git rev-parse @{u})" = "$rev" ] || {

    echo "Upstream has changed"

    ## Rebasing would be incorrect, since it would rewrite the
    ## (already published) release branch commits.
    ## Ref eg https://lists.gnu.org/r/emacs-devel/2014-12/msg01435.html
    ## Instead, we throw away what we just did, and do the merge again.
    echo "Resetting..."
    git reset --hard "$rev"

    echo "Pulling..."
    git pull --ff-only || die "pull error"

    merge

    ## If the merge finished ok again, we don't bother doing a second
    ## build and test.
}

echo "Pushing..."
git push || die "push error"


exit 0

### automerge ends here