Commit Reverser - Reverses Git Commits

commit-reverser.ts

#!/bin/bash
# to run: ./commit-reverser <first_commit>
# - creates a new branch, based on the parent of the provided commit, with the commits from HEAD 
#   to first-commit applied in reverse order
  

set -e

if [ -z "$1" ]; then
    echo "Usage: $0 <first_commit>"
    exit 1
fi

first_commit=$1

# Get the name of the original branch
original_branch_name=$(git rev-parse --abbrev-ref HEAD)

# Get the parent commit of the first commit
first_commit_parent=$(git rev-parse "${first_commit}^")

# Create a new branch based on the parent commit of the first commit
reverse_branch_name="${original_branch_name}-reversed"
git checkout -b "${reverse_branch_name}" "${first_commit_parent}"

# Perform a squash merge of the commits between the first commit and the tip of the original branch
git merge --squash "${original_branch_name}" --no-commit

# Commit the squash merge
last_commit=$(git rev-parse "${original_branch_name}")
merge_commit_message=$(git show -s --format=%s "${last_commit}")
git commit -m "${merge_commit_message} - reversed"

# Revert the commits in reverse order from the last commit to the first commit, excluding the first commit
for commit in $(git rev-list "${first_commit}..${original_branch_name}" | grep -v "${first_commit}"); do
  git checkout "${reverse_branch_name}"
  git revert --no-edit "${commit}"
done

echo "Created branch ${reverse_branch_name} with squash merge of ${original_branch_name} from ${first_commit} to ${last_commit} and reverted commits in reverse order from ${last_commit} to ${first_commit}, excluding the first commit."