#!/bin/bash
set -o errexit
gem="$1"
description="$2"
[ -z "$gem" ] && echo "No gem" >&2 && exit 1
[ -z "$description" ] && echo "No description" >&2 && exit 1
projectdir="${projectdir:-${PWD}}"
projectname="${projectdir##*/}"

[ ! -d "$projectdir/.git" ] && echo "No git repository" >&2 && exit 1

function finish()
{
  cd "$projectdir"
  git worktree prune "$tmp"
  rm -rf "$tmp"
}

git fetch
tmp="$(mktemp -d -t "${projectname}-update-worktree")"
git worktree add "$tmp" origin/master
trap finish EXIT

cd "$tmp"

rbenv install --skip-existing
gem install bundle
bundle update --conservative $gem
new_version="$(git diff -- Gemfile.lock | perl -n -e"/\+ *${gem} \((.*)\)/ && print \$1")"
old_version="$(git diff -- Gemfile.lock | perl -n -e"/\- *${gem} \((.*)\)/ && print \$1")"
[ -z "$new_version" ] && echo "No new_version" >&2 && exit 1
[ -z "$old_version" ] && echo "No old_version" >&2 && exit 1
branch="update-${gem}-$new_version"
commit_message="${gem}: $old_version -> $new_version"
git checkout -b $branch
git commit -a -m "$commit_message"
git push origin $branch
hub pull-request -m "$commit_message

**Context**

$description

**Changes**

\`\`\`
bundle update --conservative $gem
\`\`\`"