#!/bin/bash
set -euo pipefail

git fetch --tags

last_tag=$(git tag --sort=version:refname | grep -E '\d+\.\d+\.\d+' | tail -1)

a=( ${last_tag//./ } )

major=${a[0]}
minor=${a[1]}
patch=${a[2]}

case ${1:-} in
  major)
    ((major++))
    minor=0
    patch=0
    ;;
  minor)
    ((minor++))
    patch=0
    ;;
  patch)
    ((patch++));;
  *)
    echo "Usage: $0 [major|minor|patch]"
    exit 1
    ;;
esac

git log --first-parent --format=%s $last_tag..HEAD > changes.txt

if [[ ! -s changes.txt ]]
then
  echo "No changes since last tag $last_tag"
  exit 1
fi

new_tag="$major.$minor.$patch"
git tag "$new_tag" -F changes.txt
echo "Changes since last tag $last_tag:"
cat changes.txt | sed -E 's/(.*)/  \1/'
echo "Tagged $new_tag ; use \`git push --tags\` to push to server"