git-autosave

#!/usr/bin/env bash

set -eu

case "${1:-now}" in
  now) ;;
  log) git reflog 'AUTOSAVE@{now}'; exit 0 ;;
  expire) git reflog expire AUTOSAVE; exit 0 ;;
  *) echo "git autosave [now,log,expire]"; exit 1 ;;
esac

orig_index="$(git rev-parse --git-path index)"

export GIT_INDEX_FILE="$(git rev-parse --git-path autosave-index)"

[ -e "${GIT_INDEX_FILE}" ] \
  || cp "${orig_index}" "${GIT_INDEX_FILE}"

git add -u

tree="$(git write-tree)"

[ -e "$(git rev-parse --git-path AUTOSAVE)" ] \
  && git diff AUTOSAVE --quiet --exit-code \
  && exit 0 \
  || true

commit="$(git commit-tree -m autosave -p HEAD "${tree}")"

git update-ref AUTOSAVE "${commit}" --create-reflog