#!/bin/bash
# This script deletes local branches that have been squash-merged to the main branch
# Inspiration: https://github.com/not-an-aardvark/git-delete-squashed
#
# Usage: git-delete-squashed [remote]

# sometimes people use 'upstream'
remote=${1:-origin}

# could be master or main, depending on local political opinion advances
main_branch=$(git symbolic-ref refs/remotes/$remote/HEAD | xargs basename)

# get all local branches, these are the candidates to delete
git for-each-ref refs/heads/ '--format=%(refname:short)' | while read -r branch; do
  # find the common ancestor
  ancestor=$(git merge-base $branch $main_branch)

  # get the tree for the common ancestor
  tree_id=$(git rev-parse $branch^{tree})

  # generate a commit
  commit_tree=$(git commit-tree $tree_id -p $ancestor -m "delete branch $branch")

  # find if the commit is applied to main
  cherry=$(git cherry $main_branch $commit_tree)

  # cherry starts with - if it is already applied to main
  if [[ $cherry == -* ]]; then
    # delete the branch and print it to the user
    (set -x; git branch -D $branch)
  fi
done