#!/bin/bash

branch=()
if [ "X$1" = 'X-b' ]; then
        branch=( -b "$2" )
        shift 2
fi

gitk --merge -- "$@" &

tools_dir=$(dirname "$0")

hc=()
mc=()
cc=()
cformat='%(trailers:only=no,valueonly,unfold,key=signed-off-by)%aN <%aE>%n%cN <%cE>'

read -r -a head_commits -p 'HEAD commit(s): '
for c in "${head_commits[@]}"; do
	if ! git rev-parse --verify "$c" >/dev/null; then
		printf 'Unknown commit %s\n' "$c"
		exit 1
	fi
	hc+=( "$(git log -1 --format='%h ("%s")' "$c")" )
	readarray -t -O "${#cc[@]}" cc < <(git log -1 --format="$cformat" "$c" | sort -u)
done
hcs=''
if [ "${#hc[@]}" -gt 1 ]; then
	hcs='s'
fi

read -r -a head_branches -p 'HEAD branch(es): '

hb=( "${head_branches[@]/%/,}" )
hb[-1]=${hb[-1]%,}
if [ "${#hb[@]}" -gt 2 ]; then
	hb[-2]=${hb[-2]/%,/ and}
fi
hbs=''
if [ "${#hb[@]}" -gt 1 ]; then
	hbs='s'
fi

printf -v subject 'manual merge of the BRANCH tree with the %s tree%s' \
	"${hb[*]}" "$hbs"

read -r -a merge_commits -p 'MERGE_HEAD commit(s): '
for c in "${merge_commits[@]}"; do
	if ! git rev-parse --verify "$c" >/dev/null; then
		printf 'Unknown commit %s\n' "$c"
		exit 1
	fi
	mc+=( "$(git log -1 --format='%h ("%s")' "$c")" )
	readarray -t -O "${#cc[@]}" cc < <(git log -1 --format="$cformat" "$c" | sort -u)
done
mcs=''
if [ "${#mc[@]}" -gt 1 ]; then
	mcs='s'
fi

printf -v files '  %s\n' "$@"
conf='a conflict'
if [ "$#" -gt 1 ]; then
	conf='conflicts'
fi

"$tools_dir/message_helper" "${branch[@]}" "$subject" "${cc[@]}" <<EOF
FIXME: Add owner of second tree to To:
       Add author(s)/SOB of conflicting commits.

Today's linux-next merge of the BRANCH tree got $conf in:

$files
between commit$hcs:

$(printf '  %s\n' "${hc[@]}")

from the ${hb[*]} tree$hbs and commit$mcs:

$(printf '  %s\n' "${mc[@]}")

from the BRANCH tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging.  You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.
EOF

exit 0