git-fixup

#!/usr/bin/env bash

set -eu

default_branch=$(git default-branch)

if ! [ $# -eq 0 ]; then
  git commit --fixup "$1"
else
  git --no-pager log $default_branch.. --pretty=format:"%h  %s" |
    selecta |
    awk '{print $1}' |
    { read commit; git commit --fixup $commit; }
fi