git-amend.sh

#!/bin/sh

# It will only work if there is something staged and something unstaged, but it's just a proof of concept :)

TARGET=$1
git stash --keep-index
git stash
ORIGINAL=$(git show -s --pretty=%H)
git reset --hard $TARGET
git stash pop
git commit -a --amend
for h in $(git log $TARGET..$ORIGINAL --reverse --pretty=%H); do git cherry-pick $h; done
git stash pop