git_restore_for_older_git.sh

#!/bin/bash

# This allows for a "simple squash". This will be *greatly* simplified once
# newer version of Git (with `git restore`) are more widly available.

# Motivation behind this is to make a simple, commit-info-losing "squash" that
# helps Reviewable not make multiple revs:
# https://github.com/Reviewable/Reviewable/issues/592

# To run in shell, copy everything, including parentheses.

( set -eux;
if [[ -n "$(git status --porcelain)" ]]; then
  echo "You have changes in your tree (staged / unstaged). Stash them before using this."
  exit 1
fi
# You're on your feature branch.
work_rev=$(git rev-parse --short HEAD)
set +x
echo
echo "If you encounter issues, be sure to reset:"
echo
echo "   git reset --hard ${work_rev}"
echo
echo "Or use 'git reflog'"
echo
set -x
master_rev=$(git merge-base upstream/master ${work_rev})
# Reset to ref and worktree to current upstream master.
git reset --hard ${master_rev}
# Reverse so that we can show files that should be deleted / renamed.
# (For now, we will delete everything.)
files_from_prev=$(git diff --name-only ${work_rev}..${master_rev})
rm -f ${files_from_prev}
# Now reset all files to previous commit.
git checkout ${work_rev} -- :/
# Stage them for easy diff'ing.
git add -A :/
# Ensure we have zero differences now.
git diff ${work_rev}
# Now commit.
)