Enable helmfile-diff to pass the output format to helm-diff (#1784)

* tests: fix vagrant test run

* feat: added an option to specify the different diff output format

* renamed diff-output to output

* renamed diff-output to output

Co-authored-by: Andrey Tuzhilin <andrey@zelf.co>

Vagrantfile

@@ -1,11 +1,11 @@
 Vagrant.configure("2") do |config|
-  config.vm.box = "ubuntu/xenial64"
+  config.vm.box = "ubuntu/focal64"
   config.vm.hostname = "minikube.box"
   config.vm.provision :shell, privileged: false,
     inline: <<-EOS
       set -e
       sudo apt-get update
-      sudo apt-get install -y make docker.io=18.09.7-*
+      sudo apt-get install -y make docker.io
       sudo systemctl start docker
       sudo usermod -G docker $USER
       cd /vagrant/.circleci