git-amend.sh

#!/bin/bash
set -e

# Boilerplate template reference:
# https://github.com/oxyc/bash-boilerplate/blob/master/script.sh

sha1=""
version="0.1"

usage() {
    echo -n "$(basename $0) [OPTION]... [SHA1]

Commit index then immediately squash into target SHA1.

Options:
  -h, --help        Display this help and exit
      --version     Output version information and exit
"
}

# Print help if no arguments were passed.
[[ $# -eq 0 ]] && set -- "--help"

# Read the options and set stuff
while [[ $1 = -?* ]]; do
  case $1 in
    -h|--help) usage >&2; exit 0 ;;
    --version) echo "$version"; exit 0 ;;
    *) echo "Invalid option: $1" >&2; exit 1 ;;
  esac
  shift
done

sha1=$1
shift

set -x
git commit --fixup $sha1
git rebase -i -p --autosquash $sha1~2