Script to squash the last Git commit

git_squash_last.sh

#!/bin/bash -e

HEAD_COMMIT_MESSAGE=$(git log --format=%B -1 HEAD)

# For safety. Our use-case is usually to always just squash into a commit
# that's associated with an active change. We really don't want lose our head
# and accidentally squash something that wasn't intended to be squashed.
if [[ "${HEAD_COMMIT_MESSAGE}" != SQUASH* ]]; then
    echo "SQUASH: Commit to be squashed should have 'SQUASH' as its commit-message."
    exit 1
fi

_FILEPATH=$(mktemp)
git log --format=%B -1 HEAD~1 >"${_FILEPATH}"

echo "Initial head: $(git rev-parse HEAD)"

git reset --soft HEAD~2 >/dev/null

echo "Head after reset: $(git rev-parse HEAD)"

git commit -F $_FILEPATH >/dev/null
rm $_FILEPATH

echo "Head after commit: $(git rev-parse HEAD)"

echo

# Remember to alias this script as SQUASH_LAST.