squash-and-merge.sh

squash-and-merge.sh

#!/bin/bash
set -eux -o pipefail

# Usage
#   repository=<...> branch=<...> message=<...> bash squash-and-merge.sh

# validate arguments
[ -z "${repository:-}" ] && { echo "required 'repository'"; exit 1; }
[ -z "${branch:-}" ] && { echo "required 'branch'"; exit 1; }
[ -z "${message:-}" ] && { echo "required 'message'"; exit 1; }

# create temporary directory
tmp_dir=$(mktemp -d)
trap 'rm -rf -- "$tmp_dir"' EXIT

# clone repository
git clone "$repository" "$tmp_dir"
cd "$tmp_dir"

# find default branch
default_branch=$(git rev-parse --abbrev-ref HEAD)

# fetch branch
git fetch origin "$branch"
git checkout -b "$branch" "origin/$branch"

# verify branch is up-to-date (cf. https://stackoverflow.com/questions/20433867/git-ahead-behind-info-between-master-and-branch)
if ! [ "$(git rev-list --left-only --count "$default_branch...HEAD")" = "0" ]; then
  echo "branch '$branch' is not up-to-date to '$default_branch'"
  exit 1
fi

# extract git log
message_body=$(git log --pretty='format:* %s%n' --reverse "$default_branch...HEAD")

# squash commits
git reset "$default_branch"
git add .
git commit -F - <<EOF
${message}

${message_body}
EOF

# confirm
git diff --name-only "$default_branch"
git --no-pager log "$default_branch"...HEAD

echo -n "Are you sure to force push? [y/n] "
read -e -r -n 1
case "$REPLY" in
  y) ;;
  *) echo "canceled";  exit 1 ;;
esac

# force push
git push origin "$branch" --force