Refactor: split out update process from docker test

script/docker_test.rb

@@ -0,0 +1,15 @@
+def run_or_fail(command)
+  pid = Process.spawn(command)
+  Process.wait(pid)
+  exit 1 unless $?.exitstatus == 0
+end
+
+unless ENV['NO_UPDATE']
+  run_or_fail("git remote update")
+
+  checkout = ENV['COMMIT_HASH'] || "HEAD"
+  run_or_fail("git checkout #{checkout}")
+  run_or_fail("bundle")
+end
+
+run_or_fail("bundle exec rake docker:test")