update auto upgrade script to work with packages plus direct from repo

script/auto_upgrade.rb

@@ -7,6 +7,13 @@
 # It can be run as any user that has access to /opt/postal and that can run
 # commands as postal.
 
+CHANNEL = ARGV[0] || "stable"
+
+unless ['beta', 'stable'].include?(CHANNEL)
+  puts "Channel must be either 'stable' or 'beta'"
+  exit 1
+end
+
 def run(command, options = {})
   if system(command)
     # Good.
@@ -19,11 +26,19 @@ end
 puts "Stopping current Postal instance"
 run "postal stop", :exit_on_failure => false
 
+if File.exist?("/opt/postal/app/.git")
   puts "Getting latest version of repository"
   run "cd /opt/postal/app && git pull"
+else
+  puts "Backing up previous application files"
+  run "rm -Rf /opt/postal/app.backup"
+  run "cp -R /opt/postal/app /opt/postal/app.backup"
+  puts "Downloading latest version of application"
+  run "wget https://postal.atech.media/packages/#{CHANNEL}/latest.tgz -O - | tar zxpv -C /opt/postal/app"
+end
 
 puts "Installing dependencies"
-run "postal bundle /opt/postal/app/vendor/bundle"
+run "postal bundle /opt/postal/vendor/bundle"
 
 puts "Upgrading database & assets"
 run "postal upgrade"