#! /bin/bash
# Copyright (C) 2022 Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
#
# You may use this file under the terms of the 3-clause BSD license.

gitdir=$(git rev-parse --git-dir) || exit

if ! git diff --quiet HEAD; then
    echo "Working directory or index not clean." >&2
    exit 1
fi

rbdir=$gitdir/rebase-merge
if ! test -d "$rbdir"; then
    echo "No rebase ongoing?" >&2
    exit 1
fi

onto=$(<"$rbdir/onto") || exit
todo=$rbdir/git-rebase-todo

git log --reverse --pretty="tformat:pick %h %s" $onto.. > "$todo.new" || exit
(echo "break"; echo; cat "$todo") >> "$todo.new" || exit

mv "$todo" "$todo.old" || exit
mv "$todo.new" "$todo" || exit
if ! git rebase --edit-todo; then
    mv "$todo.old" "$todo"
    exit 1
fi
if ! test -s "$todo"; then
    echo "Empty todo; canceling rewind." >&2
    mv "$todo.old" "$todo"
    exit 1
fi
rm "$todo.old"
: > "$rbdir/done"

git reset --hard $onto || exit
git rebase --continue || exit