Easy squash method for squashing a lot of commits and conflict-proof

git-squash.sh

# assume starting branch is master, and we want to squash a bunch of commits from original_messy_branch
git checkout master

# create a new branch from master
git checkout -b new_clean_branch

# apply all changes from original_messy_branch to new_clean_branch either with
git merge original_messy_branch
# and then, forget the commits but have the changes staged for commit
git reset --soft master        

# or
git merge --squash original_messy_branch

git commit -m "Squashed changes from original_messy_branch"

# For pull requests
# rename local original_messy_branch to something else
git checkout master
git branch -m original_messy_branch original_messy_branch_still_messy

# rename new_clean_branch to original_messy_branch
git branch -m new_clean_branch original_messy_branch

# force push original_messy_branch (former new_clean_branch)
git checkout original_messy_branch
git push -f origin original_messy_branch

# Reference:
# https://stackoverflow.com/a/44789323/9214463