Upgrade mastodon via git

upgrade-mastodon.sh

# as root
systemctl stop mastodon-web mastodon-sidekiq mastodon-streaming

su - mastodon
cd live

# as mastodon user, in its live direcotry
export MASTODON_VER=v4.3.7
export RAILS_ENV=production

git fetch && git checkout ${MASTODON_VER}
bundle install
yarn install
bundle exec rails db:migrate
bundle exec rails assets:precompile

exit

# assuming you are root now
systemctl start mastodon-web mastodon-sidekiq mastodon-streaming

### You might need to install / update ruby, if you run into errors like
### rbenv: version `x.x.x' is not installed (set by /home/mastodon/live/.ruby-version)
### Then:
git -C /home/mastodon/.rbenv/plugins/ruby-build pull
export RUBY_CONFIGURE_OPTS=--with-jemalloc 
rbenv install x.x.x