Re-download and recompile Gitaly in tests if the version changed

spec/support/test_env.rb

@@ -123,7 +123,7 @@ module TestEnv
     socket_path = Gitlab::GitalyClient.address('default').sub(/\Aunix:/, '')
     gitaly_dir = File.dirname(socket_path)
 
-    unless File.directory?(gitaly_dir) || system('rake', "gitlab:gitaly:install[#{gitaly_dir}]")
+    unless !gitaly_needs_update?(gitaly_dir) || system('rake', "gitlab:gitaly:install[#{gitaly_dir}]")
       raise "Can't clone gitaly"
     end
 
@@ -252,4 +252,15 @@ module TestEnv
       cleanup && init unless reset.call
     end
   end
+
+  def gitaly_needs_update?(gitaly_dir)
+    gitaly_version = File.read(File.join(gitaly_dir, 'VERSION')).strip
+
+    # Notice that this will always yield true when using branch versions
+    # (`=branch_name`), but that actually makes sure the server is always based
+    # on the latest branch revision.
+    gitaly_version != Gitlab::GitalyClient.expected_server_version
+  rescue Errno::ENOENT
+    true
+  end
 end