rewinding interactive rebases

[Oswald Buddenhagen <oswald.buddenhagen@gmx.de>]

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heya,

this post is basically a continuation of 
https://public-inbox.org/git/CAE1pOi1XtrWqG7mOdrNt10YoZG0LOAB7i9cc1Gi8oWhULxE57A@mail.gmail.com/ 
("Is there any way to "interrupt" a rebase?"), but i thought it's 
probably better to start a new thread rather than to revive a zombie.

the basic problem is that during significant reworks of (complex) 
branches, one will inevitably find oneself in the situation of wanting 
to "go back" in the process. fixup commits aren't always optimal, as 
subsequent re-ordering may cause conflicts. doing the amend in the right 
place to start with cuts away one of the conflict resolutions.

the solution to this is actually rather simple, as demonstrated by the 
attached script.

somebody feels like rewriting this as a nice 'git rebase --rewind' 
subcommand?

thanks

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#! /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